Question

How mny integer less than 100 where reverse of n is?

Answer 1

Lets say, n=10x+y as 100>n>10 so , if we reverse the digit , n becomes 10y+x but according to Qs, 10y+x = n-9 => 10y+x = 10x+y - 9 => 9(x-y) = 9 => x-y =1 hence we need to find out the 2 digits where diff is 1 so, the nos are , 21(12) , 32(23) , 43(34) , 54(45) , 65(56) , 76(67), 87(78) , 98(89) choice is D