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MCQ practice · SSC Higher Mathematics Board questions · Chapter 7: Infinite Series

Rajshahi Board 2023

Regarding the series 0.032 + 0.00032 + 0.0000032 + …, which is correct?

  1. i. the series is a geometric series
  2. ii. the common ratio is 0.01
  3. iii. the sum to infinity is 32/99

Think it through first, then pick an option.

  1. a i and ii
  2. b i and iii
  3. c ii and iii
  4. d i, ii and iii
Answer and explanation

Correct answer: a i and ii

r = 0.00032/0.032 = 0.01; S∞ = 0.032/0.99 = 32/990, so iii is false.

Why the other options are wrong

  • b i and iii: iii is false: the sum is 32/990 = 16/495, not 32/99; and ii is true, which is left out.
  • c ii and iii: iii is false (the sum is 32/990) and i is true, which is left out.
  • d i, ii and iii: iii is false: 0.032/0.99 = 32/990, not 32/99.