Question Video: Dividing a Length into a Three Part Ratio Mathematics

>Divide 72 centimeters in the ratio 2 : 3 : 1.


Video Transcript

Divide 72 centimeters in the ratio two to three to one.

Let’s recall one of the methods we have for sharing into a ratio. It’s called the add-divide-multiply method. In this method, the first thing we do is we add the numbers in our ratio. This will tell us the total number of parts we’re sharing into. Our ratio is two to three to one. And two plus three plus one is six. So we have a total of six parts.

Step two is to divide the amount we’ve been given by this number. This will tell us what one part is worth. We’re dividing 72 then by six, and that gives us 12. Of course, we’re actually working in centimeters. So we can say that one part is worth 12 centimeters.

Our final step is to multiply each bit of the ratio by this number. Essentially, if we know the value of one part, we can find the value of two by timesing it by two, we can find the value of three by timesing it by three, and so on. Two multiplied by 12 is 24, so the first bit we get is 24 centimeters. Three times 12 is 36, so our second bit is 36 centimeters. Then one multiplied by 12, which we don’t really need to do but we’ll do for completion, is 12. And the third bit is 12 centimeters.

When we divide 72 centimeters in the ratio two to three to one, we get 24 centimeters, 36 centimeters, and 12 centimeters. In fact, 24 plus 36 plus 12 gives us the original 72 as we required. So we know that we’ve probably done this correctly.

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