Question

Hwo many two digit numbers are divisible by 6?

Answer 1

The first two digit no. divisible by 6 is 12 and the last two digit no. divisible by 6 is 96
So let a=12 ,d=6, $a_n$=96
Now we know that

$a_n=a+(n-1)d$
96=12+(n-1)6
84=(n-1)6
n-1=14
n=15
hence total no of two digits no. divisible by 6 = 15