Question

The sum of the digits of a number lying between 10 and 100 is 9. If the number is multiplied by 7 it becomes 4 times the number obtained by writing the digits in the reverse order. find the number

Answer 1

first we will think of no. whose sum is 9
No. can be 72 ,81,36,90,54 etc
now we will apply the question theory on all no.
By this we will find that 36 is the no. which proves the following