IXL | Divisibility rules: word problems

Matt works as a dog walker. He walked 12 dogs today and took the same number of dogs on each walk. How many dogs could Matt have taken on each walk?

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question

There are 99 sixth-graders at Liz's school. There are the same number of students in each sixth-grade class. How many sixth-grade classes could there be at Liz's school?

key idea

A number is divisible by 2 if its ones digit is 0, 2, 4, 6, or 8.

A number is divisible by 6 if it is divisible by both 2 and 3.
It is divisible by 2 if its ones digit is 0, 2, 4, 6, or 8.
It is divisible by 3 if the sum of its digits is divisible by 3.

A number is divisible by 10 if its ones digit is 0.

A number is divisible by 3 if the sum of its digits is divisible by 3.

solution

Which number evenly divides 99? Try each number.

First try the "divisible by 2" rule on 99.

Look at the ones digit:

The ones digit is 9.

The rule says that 99 is not divisible by 2.

Next try the "divisible by 6" rule on 99.

First check if 99 is divisible by 2.

Look at the ones digit:

The ones digit is 9.

So, the number is not divisible by 2.

The rule says that 99 is not divisible by 6.

Next try the "divisible by 10" rule on 99.

Look at the ones digit:

The ones digit is 9.

The rule says that 99 is not divisible by 10.

Finally, try the "divisible by 3" rule on 99.

Find the sum of the digits:

9 + 9 = 18

18 is divisible by 3.

The rule says that 99 is divisible by 3.

99 is divisible by 3. There could be 3 sixth-grade classes at Liz's school.

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Lesson: Divisibility rules

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