UPSC Prelims 2008·GS1·science-and-technology·science and technology

What is the number of terms in the series 117, 120, 123, 126, ..., 333?

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Last updated 23 May 2026, 3:31 pm IST
  1. A72
  2. B73Correct
  3. C76
  4. D79

Explanation

The given series 117, 120, 123, 126, ..., 333 is an Arithmetic Progression because there is a constant common difference between consecutive terms. In this series: The first term (a) is 117. The common difference (d) is 120 minus 117, which equals 3. The last term (l) is 333. The formula to find the number of terms (n) in an Arithmetic Progression is: n = ((Last term minus First term) divided by Common difference) plus 1. Applying the values: n = ((333 minus 117) divided by 3) plus 1. n = (216 divided by 3) plus 1. n = 72 plus 1. n = 73. Therefore, the number of terms in the series is 73. The correct option is B.
science-and-technology: What is the number of terms in the series 117, 120, 123, 126, ..., 333?
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