Question

The first three terms of an AP respectively are 3y – 1, 3y + 5 and 5y + 1. Then y equals:

(A) –3
(B) 4
(C) 5
(D) 2

Answer 1

The first three terms of an AP are 3y – 1, 3y + 5 and 5y + 1 respectively

We need to find the value of y.
We know that if a, b and c are in AP, then:
b − a = c − b ⇒ 2b = a + c

∴2(3y+5) = 3y − 1 + 5y + 1

⇒6y + 10 = 8y

⇒10 = 8y −6y

⇒2y = 10

⇒y = 5

Hence, the correct option is C.