Addition of multiples of ten quiz online. This is an interactive online math quiz online in which kids review how to add multiples of ten. For example, adding 10 + 20, 60 + 40 etc. When adding two multiples of ten, the ones place usually adds up to zero since it contains zero for both numbers. The trick henceforth lies in adding the numbers in the tens place. A smart way to go about it is to assume that the ones (or units) place will always be zero and focus on adding the two numbers in the tens place. This is an online for kids in kindergarten, 1st , 2nd and 3rd grades.