Question

For what value of k will be k+9 ,2k-1 and 2k +7 are consecutive terms of an ap?

Answer 1

In Ap common difference are equal
So
2k-1-(k+9)=2k+7-(2k-1)
2k-1-k-9=2k+7-2k+1
k-10=8
k=18

Answer 2

2b=a+c
2(2k-1)=k+9+2k+7
4k-2= k+9+2k+7
4k-3=3k+16
4k-3k=16+2
K=18

Hope it helps...