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NCERT Solutions › Mathematics › Chapter 9

Chapter 9: Sequences & Series

NCERT Solutions for CBSE Class 10 Mathematics — 171 solved questions with detailed explanations.

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Solved Questions

Q1. The sum of infinite GP 1 + 1/2 + 1/4 + 1/8 + ... is:

Difficulty: Easy · Topic: GP Sum

Solution

S = a/(1-r) = 1/(1-1/2) = 1/(1/2) = 2.

Q2. The nth term of the sequence 2, 5, 8, 11, ... is:

Difficulty: Easy · Topic: nth Term

Solution

AP with a=2, d=3. T_n = a+(n-1)d = 2+3(n-1) = 3n-1.

Q3. The sum of first 20 terms of an AP with first term 5 and common difference 3 is:

Difficulty: Easy-Medium · Topic: AP Sum

Solution

S₂₀ = (20/2)[2(5) + 19(3)] = 10[10 + 57] = 10 × 67 = 670.

Q4. The sum of 15 terms of an AP with a=3, d=2 is:

Difficulty: Easy-Medium · Topic: AP Sum

Solution

S = n/2[2a+(n-1)d] = 15/2[6+28] = 255.

Q5. The sum of 10 terms of an AP with a=1, d=4 is:

Difficulty: Easy-Medium · Topic: AP Sum

Solution

S = n/2[2a+(n-1)d] = 10/2[2+36] = 190.

Q6. The sum of 20 terms of an AP with a=10, d=-2 is:

Difficulty: Easy-Medium · Topic: AP Sum

Solution

S = n/2[2a+(n-1)d] = 20/2[20+-38] = -180.

Q7. The sum of 12 terms of an AP with a=5, d=3 is:

Difficulty: Easy-Medium · Topic: AP Sum

Solution

S = n/2[2a+(n-1)d] = 12/2[10+33] = 258.

Q8. Sum of 100 terms of AP with a=1, d=1 is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = n/2[2a+(n-1)d] = 100/2[2+99] = 5050.

Q9. Sum of 20 terms of AP with a=2, d=3 is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = n/2[2a+(n-1)d] = 20/2[4+57] = 610.

Q10. Sum of 10 terms of AP with a=5, d=5 is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = n/2[2a+(n-1)d] = 10/2[10+45] = 275.

Q11. Sum of 15 terms of AP with a=3, d=2 is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = n/2[2a+(n-1)d] = 15/2[6+28] = 255.

Q12. Sum of 10 terms of AP with a=1, d=4 is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = n/2[2a+(n-1)d] = 10/2[2+36] = 190.

Q13. Sum of 20 terms of AP with a=10, d=-2 is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = n/2[2a+(n-1)d] = 20/2[20+-38] = -180.

Q14. Sum of 12 terms of AP with a=5, d=3 is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = n/2[2a+(n-1)d] = 12/2[10+33] = 258.

Q15. Sum of 25 terms of AP with a=7, d=2 is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = n/2[2a+(n-1)d] = 25/2[14+48] = 775.

Q16. Sum of 50 terms of AP with a=1, d=2 is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = n/2[2a+(n-1)d] = 50/2[2+98] = 2500.

Q17. Sum of 8 terms of AP with a=4, d=6 is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = n/2[2a+(n-1)d] = 8/2[8+42] = 200.

Q18. Sum of 10 terms of GP with a=1, r=2 is:

Difficulty: Easy-Medium · Topic: GP

Solution

S = a(r^n-1)/(r-1) = 1(2^10-1)/(2-1) = 1023.

Q19. Sum of 8 terms of GP with a=3, r=2 is:

Difficulty: Easy-Medium · Topic: GP

Solution

S = a(r^n-1)/(r-1) = 3(2^8-1)/(2-1) = 765.

Q20. Sum of 6 terms of GP with a=1, r=3 is:

Difficulty: Easy-Medium · Topic: GP

Solution

S = a(r^n-1)/(r-1) = 1(3^6-1)/(3-1) = 364.

Q21. Sum of 5 terms of GP with a=2, r=3 is:

Difficulty: Easy-Medium · Topic: GP

Solution

S = a(r^n-1)/(r-1) = 2(3^5-1)/(3-1) = 242.

Q22. Sum of 7 terms of GP with a=5, r=2 is:

Difficulty: Easy-Medium · Topic: GP

Solution

S = a(r^n-1)/(r-1) = 5(2^7-1)/(2-1) = 635.

Q23. Sum of 5 terms of AP (a=1, d=-3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(1)+(5-1)(-3)] = -25.

Q24. Sum of 10 terms of AP (a=1, d=-3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(1)+(10-1)(-3)] = -125.

Q25. Sum of 15 terms of AP (a=1, d=-3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(1)+(15-1)(-3)] = -300.

Q26. Sum of 20 terms of AP (a=1, d=-3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(1)+(20-1)(-3)] = -550.

Q27. Sum of 25 terms of AP (a=1, d=-3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(1)+(25-1)(-3)] = -875.

Q28. Sum of 5 terms of AP (a=1, d=-2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(1)+(5-1)(-2)] = -15.

Q29. Sum of 10 terms of AP (a=1, d=-2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(1)+(10-1)(-2)] = -80.

Q30. Sum of 15 terms of AP (a=1, d=-2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(1)+(15-1)(-2)] = -195.

Q31. Sum of 20 terms of AP (a=1, d=-2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(1)+(20-1)(-2)] = -360.

Q32. Sum of 25 terms of AP (a=1, d=-2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(1)+(25-1)(-2)] = -575.

Q33. Sum of 5 terms of AP (a=1, d=-1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(1)+(5-1)(-1)] = -5.

Q34. Sum of 10 terms of AP (a=1, d=-1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(1)+(10-1)(-1)] = -35.

Q35. Sum of 15 terms of AP (a=1, d=-1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(1)+(15-1)(-1)] = -90.

Q36. Sum of 20 terms of AP (a=1, d=-1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(1)+(20-1)(-1)] = -170.

Q37. Sum of 25 terms of AP (a=1, d=-1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(1)+(25-1)(-1)] = -275.

Q38. Sum of 5 terms of AP (a=1, d=1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(1)+(5-1)(1)] = 15.

Q39. Sum of 10 terms of AP (a=1, d=1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(1)+(10-1)(1)] = 55.

Q40. Sum of 15 terms of AP (a=1, d=1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(1)+(15-1)(1)] = 120.

Q41. Sum of 20 terms of AP (a=1, d=1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(1)+(20-1)(1)] = 210.

Q42. Sum of 25 terms of AP (a=1, d=1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(1)+(25-1)(1)] = 325.

Q43. Sum of 5 terms of AP (a=1, d=2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(1)+(5-1)(2)] = 25.

Q44. Sum of 10 terms of AP (a=1, d=2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(1)+(10-1)(2)] = 100.

Q45. Sum of 15 terms of AP (a=1, d=2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(1)+(15-1)(2)] = 225.

Q46. Sum of 20 terms of AP (a=1, d=2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(1)+(20-1)(2)] = 400.

Q47. Sum of 25 terms of AP (a=1, d=2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(1)+(25-1)(2)] = 625.

Q48. Sum of 5 terms of AP (a=1, d=3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(1)+(5-1)(3)] = 35.

Q49. Sum of 10 terms of AP (a=1, d=3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(1)+(10-1)(3)] = 145.

Q50. Sum of 15 terms of AP (a=1, d=3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(1)+(15-1)(3)] = 330.

Q51. Sum of 20 terms of AP (a=1, d=3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(1)+(20-1)(3)] = 590.

Q52. Sum of 25 terms of AP (a=1, d=3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(1)+(25-1)(3)] = 925.

Q53. Sum of 5 terms of AP (a=1, d=4) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(1)+(5-1)(4)] = 45.

Q54. Sum of 10 terms of AP (a=1, d=4) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(1)+(10-1)(4)] = 190.

Q55. Sum of 15 terms of AP (a=1, d=4) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(1)+(15-1)(4)] = 435.

Q56. Sum of 20 terms of AP (a=1, d=4) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(1)+(20-1)(4)] = 780.

Q57. Sum of 25 terms of AP (a=1, d=4) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(1)+(25-1)(4)] = 1225.

Q58. Sum of 5 terms of AP (a=1, d=5) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(1)+(5-1)(5)] = 55.

Q59. Sum of 10 terms of AP (a=1, d=5) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(1)+(10-1)(5)] = 235.

Q60. Sum of 15 terms of AP (a=1, d=5) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(1)+(15-1)(5)] = 540.

Q61. Sum of 20 terms of AP (a=1, d=5) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(1)+(20-1)(5)] = 970.

Q62. Sum of 25 terms of AP (a=1, d=5) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(1)+(25-1)(5)] = 1525.

Q63. Sum of 5 terms of AP (a=1, d=6) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(1)+(5-1)(6)] = 65.

Q64. Sum of 10 terms of AP (a=1, d=6) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(1)+(10-1)(6)] = 280.

Q65. Sum of 15 terms of AP (a=1, d=6) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(1)+(15-1)(6)] = 645.

Q66. Sum of 20 terms of AP (a=1, d=6) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(1)+(20-1)(6)] = 1160.

Q67. Sum of 25 terms of AP (a=1, d=6) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(1)+(25-1)(6)] = 1825.

Q68. Sum of 5 terms of AP (a=1, d=7) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(1)+(5-1)(7)] = 75.

Q69. Sum of 10 terms of AP (a=1, d=7) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(1)+(10-1)(7)] = 325.

Q70. Sum of 15 terms of AP (a=1, d=7) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(1)+(15-1)(7)] = 750.

Q71. Sum of 20 terms of AP (a=1, d=7) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(1)+(20-1)(7)] = 1350.

Q72. Sum of 25 terms of AP (a=1, d=7) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(1)+(25-1)(7)] = 2125.

Q73. Sum of 5 terms of AP (a=2, d=-3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(2)+(5-1)(-3)] = -20.

Q74. Sum of 10 terms of AP (a=2, d=-3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(2)+(10-1)(-3)] = -115.

Q75. Sum of 15 terms of AP (a=2, d=-3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(2)+(15-1)(-3)] = -285.

Q76. Sum of 20 terms of AP (a=2, d=-3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(2)+(20-1)(-3)] = -530.

Q77. Sum of 25 terms of AP (a=2, d=-3) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(2)+(25-1)(-3)] = -850.

Q78. Sum of 5 terms of AP (a=2, d=-2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(2)+(5-1)(-2)] = -10.

Q79. Sum of 10 terms of AP (a=2, d=-2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(2)+(10-1)(-2)] = -70.

Q80. Sum of 15 terms of AP (a=2, d=-2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(2)+(15-1)(-2)] = -180.

Q81. Sum of 20 terms of AP (a=2, d=-2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(2)+(20-1)(-2)] = -340.

Q82. Sum of 25 terms of AP (a=2, d=-2) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(2)+(25-1)(-2)] = -550.

Q83. Sum of 5 terms of AP (a=2, d=-1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(2)+(5-1)(-1)] = 0.

Q84. Sum of 10 terms of AP (a=2, d=-1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(2)+(10-1)(-1)] = -25.

Q85. Sum of 15 terms of AP (a=2, d=-1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 15/2[2(2)+(15-1)(-1)] = -75.

Q86. Sum of 20 terms of AP (a=2, d=-1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 20/2[2(2)+(20-1)(-1)] = -150.

Q87. Sum of 25 terms of AP (a=2, d=-1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 25/2[2(2)+(25-1)(-1)] = -250.

Q88. Sum of 5 terms of AP (a=2, d=1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 5/2[2(2)+(5-1)(1)] = 20.

Q89. Sum of 10 terms of AP (a=2, d=1) is:

Difficulty: Easy-Medium · Topic: AP

Solution

S = 10/2[2(2)+(10-1)(1)] = 65.

Q90. AP a=1, d=-5, n=5. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-45.

Q91. AP a=1, d=-5, n=8. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-132.

Q92. AP a=1, d=-5, n=10. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-215.

Q93. AP a=1, d=-5, n=12. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-318.

Q94. AP a=1, d=-5, n=15. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-510.

Q95. AP a=1, d=-5, n=20. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-930.

Q96. AP a=1, d=-5, n=25. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-1475.

Q97. AP a=1, d=-5, n=30. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-2145.

Q98. AP a=1, d=-5, n=50. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-6075.

Q99. AP a=1, d=-4, n=5. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-35.

Q100. AP a=1, d=-4, n=8. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-104.

Q101. AP a=1, d=-4, n=10. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-170.

Q102. AP a=1, d=-4, n=12. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-252.

Q103. AP a=1, d=-4, n=15. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-405.

Q104. AP a=1, d=-4, n=20. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-740.

Q105. AP a=1, d=-4, n=25. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-1175.

Q106. AP a=1, d=-4, n=30. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-1710.

Q107. AP a=1, d=-4, n=50. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-4850.

Q108. AP a=1, d=-3, n=5. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-25.

Q109. AP a=1, d=-3, n=8. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-76.

Q110. AP a=1, d=-3, n=10. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-125.

Q111. AP a=1, d=-3, n=12. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-186.

Q112. AP a=1, d=-3, n=15. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-300.

Q113. AP a=1, d=-3, n=20. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-550.

Q114. AP a=1, d=-3, n=25. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-875.

Q115. AP a=1, d=-3, n=30. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-1275.

Q116. AP a=1, d=-3, n=50. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-3625.

Q117. AP a=1, d=-2, n=5. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-15.

Q118. AP a=1, d=-2, n=8. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-48.

Q119. AP a=1, d=-2, n=10. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-80.

Q120. AP a=1, d=-2, n=12. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-120.

Q121. AP a=1, d=-2, n=15. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-195.

Q122. AP a=1, d=-2, n=20. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-360.

Q123. AP a=1, d=-2, n=25. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-575.

Q124. AP a=1, d=-2, n=30. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-840.

Q125. AP a=1, d=-2, n=50. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-2400.

Q126. AP a=1, d=-1, n=5. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-5.

Q127. AP a=1, d=-1, n=8. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-20.

Q128. AP a=1, d=-1, n=10. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-35.

Q129. AP a=1, d=-1, n=12. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-54.

Q130. AP a=1, d=-1, n=15. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-90.

Q131. AP a=1, d=-1, n=20. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-170.

Q132. AP a=1, d=-1, n=25. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-275.

Q133. AP a=1, d=-1, n=30. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-405.

Q134. AP a=1, d=-1, n=50. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=-1175.

Q135. AP a=1, d=1, n=5. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=15.

Q136. AP a=1, d=1, n=8. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=36.

Q137. AP a=1, d=1, n=10. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=55.

Q138. AP a=1, d=1, n=12. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=78.

Q139. AP a=1, d=1, n=15. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=120.

Q140. AP a=1, d=1, n=20. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=210.

Q141. AP a=1, d=1, n=25. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=325.

Q142. AP a=1, d=1, n=30. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=465.

Q143. AP a=1, d=1, n=50. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=1275.

Q144. AP a=1, d=2, n=5. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=25.

Q145. AP a=1, d=2, n=8. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=64.

Q146. AP a=1, d=2, n=10. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=100.

Q147. AP a=1, d=2, n=12. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=144.

Q148. AP a=1, d=2, n=15. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=225.

Q149. AP a=1, d=2, n=20. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=400.

Q150. AP a=1, d=2, n=25. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=625.

Q151. AP a=1, d=2, n=30. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=900.

Q152. AP a=1, d=2, n=50. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=2500.

Q153. AP a=1, d=3, n=5. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=35.

Q154. AP a=1, d=3, n=8. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=92.

Q155. AP a=1, d=3, n=10. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=145.

Q156. AP a=1, d=3, n=12. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=210.

Q157. AP a=1, d=3, n=15. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=330.

Q158. AP a=1, d=3, n=20. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=590.

Q159. AP a=1, d=3, n=25. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=925.

Q160. AP a=1, d=3, n=30. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=1335.

Q161. AP a=1, d=3, n=50. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=3725.

Q162. AP a=1, d=4, n=5. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=45.

Q163. AP a=1, d=4, n=8. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=120.

Q164. AP a=1, d=4, n=10. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=190.

Q165. AP a=1, d=4, n=12. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=276.

Q166. AP a=1, d=4, n=15. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=435.

Q167. AP a=1, d=4, n=20. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=780.

Q168. AP a=1, d=4, n=25. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=1225.

Q169. AP a=1, d=4, n=30. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=1770.

Q170. AP a=1, d=4, n=50. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=4950.

Q171. AP a=1, d=5, n=5. Sum:

Difficulty: Easy-Medium · Topic: AP

Solution

S=n/2[2a+(n-1)d]=55.

Other Chapters in Mathematics

Ch 1: SetsCh 2: Relations & FunctionsCh 3: Trigonometric FunctionsCh 4: Principle of Mathematical InductionCh 5: Complex NumbersCh 6: Linear InequalitiesCh 7: Permutations & CombinationsCh 8: Binomial TheoremCh 10: Straight LinesCh 11: Conic SectionsCh 12: Intro to 3D GeometryCh 13: Limits & DerivativesCh 14: Mathematical ReasoningCh 15: StatisticsCh 16: Probability

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