That is the average of the first 17 multiples of 13:

Question

Question

This question was previously asked in

Bihar STET TGT (Social Science) Official Paper-I (Held On: 08 Sept, 2023 Shift 5)

Answer 1

Formula Used:

Average = (Sum of the multiples) / (Number of multiples)

Sum = (n/2) × [2a + (n - 1) d]

Where:

n is the number of terms (17 in this case),

a is the first term (13),

d is the common difference (13).

Calculation:

Now, substitute these values into the formulas:

⇒ Sum = (17/2) × (2 × 13 + (17−1) × 13)

⇒ Sum = (17/2) × (26 + 16 × 13)

⇒ Sum = (17/2) × (26 + 208)

⇒ Sum = (17/2) × 234

⇒ Sum = 17 × 117

Now, find the average:

Average = 17 × 117 / 17 = 117

∴ The correct answer is 117.