Question

What will be the 15th number in the following series of A.P.?

3, 8, 13, 18, 23, .......

1. 78
2. 63
3. 73
4. 68

Answer 1

Correct Answer - Option 3 : 73

Given:

Arithmetic progression series: 3, 8, 13, 18, 23, .......

Concept used:

To find nth term of an AP is, Tn = a + (n - 1)d

Where a is first term, n is number of terms and d is common difference

Calculation:

We can see a common difference (d) = 5

First-term (a) = 3

Thus 15th term in this series ⇒ T15 = 3 + (15 - 1)5

T₁₅ = 3 + (14)5

⇒ T15 = 3 + 70

⇒ T15 = 73

Hence, the correct answer is "73".

In in question it is said 15th number in the following series of A.P so we will not use the logic of +5 to the number.

Thus 23 + 5 = 28 this will be incorrect answer.