Question

A two digit number is such that the product of digits is 21 9 is added to number then the digits interchange the places find the number

Answer 1

The only factors of 21 is 1,3,7,21. As 1 and 21 muliply to get a product of 21, and 3 and 7 multiply to get a product of 21. When combining those digits you get 121 and 37. 37 is the only 2 digit number so therefore that would be the choice. 37 plus 9 equals 46. Once the digits interchange, which means to change places, the answer is 64.

An alternate answer for this problem would be 28.
This would work because 73 also has 2 digits that multiply to get a product of 21. 73 plus 9 equals 82. Once those digits switch places or interchange, the answer would be 28.