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 correct option is C

5

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 $\Rightarrow$ 2b = a + c
$\therefore 2(3y+5)=3y-1+5y+1$
$\Rightarrow 6y+10=8y$
$\Rightarrow 10=8y-6y$
$\Rightarrow 2y=10$
$\Rightarrow y=5$
Hence the correct option is C.