Q2/129) For how many 2 digit numbers the sum of digits is greater than the product of digits?

Solution

(x+y) > xy
or  xy - x - y < 0
x(y-1) < y

  y = 0 for all x so all multiples of 10 is a set of solution 

x < y/(y-1)

or x < 1+ 1/(y-1)
so x has to be 1

so multiples of 10 or any one of digits should be 1

that 10, 20, 30, 40,50,60,70,.80,90, 11,12,13,14,15,16,17,18,19, 21,31,41,51,61,71,81,91