SSC Selection Post 2019 PYQ — Question 63

The correct answer is option 1 i.e. 31.

Sum of n terms in an AP = $\frac{n}{2}(a+ l)$

where n is number of terms, a is first term and l is last term.

20 consecutive numbers are in AP, common difference = 1

Let the first term of this AP be x, the last term = x + 19

Now, sum of 20 terms = 20 × 21.5 = 430

⇒ $\frac{20}{2}(x+ x + 19)$ = 430

⇒ 2x + 19 = 43

⇒ 2x = 24

⇒ x = 12

Now, largest term = x + 19 = 12 + 19 = 31