Video: Finding the Factors of Given Numbers

Find all the factors of the numbers 15 and 87.

01:50

Video Transcript

Find all the factors of the numbers 15 and 87.

First of all, what are factors? They’re numbers you multiply together to get another number. Factors of 15 are all the numbers you multiply together to get 15. We know that if we multiplied one times 15, we would get 15. Can we multiply two by anything to get 15? No, because 15 is not an even number. It’s not divisible by two. 15 is divisible by three because three times five equals 15. The factors of 15 are one, 15, three, and five.

How about 87? One times 87 equals 87. 87 is an odd number. So it’s not divisible by two. 87 is divisible by three. Three times 29 equals 87. 87 can’t be divisible by four because it’s an odd number. It doesn’t end in five or zero. So 87 can’t be divisible by five. It’s not divisible by six because 87 is an odd number. Is 87 divisible by seven? No, can’t be eight; eight is an even number.

Lastly, we can check nine. Nine is not divided into 87 evenly. The four factors we found for 87 are one, 87, three, and 29.

Our question is asking for us to list the numbers that are factors of 15 and 87. That would be one, three, five, 15, 29, and 87.

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