SSC CGL 2025 Tier-I · 16 September 2025, Shift 1 · General Intelligence and Reasoning · Question 19 of 100

We transcribed this text from the pictures on a candidate's response sheet for this shift; the answer is the key SSC colour-marked on that sheet. Solution last reviewed 13 September 2026.

Where this paper and its answers come from

SSC does not publish CGL question papers or a public answer key. From 2025 the candidate response sheet prints every question and option as a picture, so the text here is transcribed from those pictures for this shift and checked against them independently; where the layout carries meaning, the picture is shown as well. Each answer is the key SSC colour-marked on that sheet. SSC released a tentative key for challenge and later its final one, both only to candidates behind a login, and the sheet does not say which of the two it carries. The solutions are written by UnlockIAS.

What is the average of 5 consecutive odd numbers starting from 13?

(a)17
(b)18
(c)20
(d)23

Answer

Why

Correct — A.
Rule: consecutive odd numbers rise by 2, and with an odd count the average is the middle term.

The five numbers: 13, 15, 17, 19, 21
Sum: 13 + 15 + 17 + 19 + 21 = 85
Average: 85 ÷ 5 = 17

The middle term, 17, gives the same answer → option (a).

Why the others are wrong

(b)
18 — 18 is the average of six odd numbers, 13 to 23: (13 + 23) ÷ 2 = 18. The question asks for five, which end at 21.
(c)
20 — 20 is even. Five consecutive odd numbers have an odd middle term, and that middle term is their average, 17.
(d)
23 — 23 is 13 + 2 × 5, one step past the fifth number, which is 13 + 2 × 4 = 21. An average also cannot exceed the largest of the five.

Concept

Consecutive odd numbers form an arithmetic progression with common difference 2. Counting from a start a, the nth one is a + 2(n − 1).

The average of an arithmetic progression is (first + last) ÷ 2. With an odd count, that is also the middle term.

Here the first is 13 and the last is 13 + 2 × 4 = 21, so the average is (13 + 21) ÷ 2 = 17.

Key facts

Counting from a start a, the nth consecutive odd number is a + 2(n − 1).
The average of an arithmetic progression is (first term + last term) ÷ 2.
With an odd number of terms, the average equals the middle term.

Study next

Sum of the first n odd numbers, which is n²Averages of consecutive even numbersRecovering the numbers when the average of consecutive numbers is given

Common traps

Taking the last term as 13 + 2 × 5 = 23 instead of 13 + 2 × 4 = 21
Counting 13 to 23 as five odd numbers when it is six

Here the item gives the first term and the count and asks for the average, so the middle term answers it without any adding.

Related PYQs

No directly related past PYQ was found.

Topic: Semantic Classification — all 59 SSC CGL questions on it, every solved shift.