Problems on Numbers - General Questions

The difference between a two-digit number and the number obtained by interchanging its digits is 18. What is the difference between the two digits?

The sum of two numbers is 23 and their product is 112. What is the sum of their squares?

The difference between a two-digit number and the number obtained by interchanging its digits is 9. What is the difference between the two digits?

A number exceeds its one-fifth by 96. What is the number?

When 4 times a number is increased by 19, the result is 119. What is the number?