Correct Answer:
B. 25
The correct answer is 25. The sequence 20, 25, 30, ..., 140 forms an arithmetic progression (AP) with the following parameters:
- First term (a) = 20
- Common difference (d) = 5
- Last term (Tₙ) = 140
We use the formula for the nth term of an AP: Tₙ = a + (n − 1)d
Substituting the values: 140 = 20 + (n − 1) × 5
- 140 − 20 = (n − 1) × 5
- 120 = (n − 1) × 5
- 120 ÷ 5 = n − 1
- 24 = n − 1
- n = 25
Options 22, 23, and 24 do not satisfy the formula, so the correct answer is 25.