How many terms are there in the sequence 20, 25, 30, …, 140?

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.