1/10 and 8/100 which is the correct sum

To add 1/10 and 8/100, they must have the same denominator.

To do this, multiply 1/10 by 10/10 (which equals one, so it doesn't change the value of the fraction).

Now you have 10/100 and 8/100. To add them, simply add the numerators and keep the denominators the same.

This results in 18/100, which can be simplified to 9/50.