Question

A number of two digits is less than 8 times the number of the product of its digits. If the number of the digit with a digit of 1 is greater than 1, then what are those numbers?

Answer 1

Well, for two digits with their product to be 8, there is only two possibilities : {1,8} and {2,4}. If we look at the differences of the 2-digit numbers formed by these two sets, we find 81−18=63 and 42−24=18. Therefore, this number is 24, as can be verified by 2×4=8 and 24+18=42 (digits are reversed).