Video: KS2-M19 • Paper 1 • Question 18

20% of 3000 = _.

03:29

Video Transcript

20 percent of 3000 equals what.

The word percent means out of 100. And it’s a way of showing parts of a whole, with 100 percent being the same as a whole. In our problem, the whole amount is 3000. And in this problem, we’re being asked to find what 20 percent of 3000 is worth. The interesting thing about problems like this is that there are often several ways we can find the answer. So how can we find 20 percent of a number?

Let’s go through two different methods that we could use. The first is to find 10 percent of 3000 and then double it to give us 20 percent. Finding 10 percent of a number is usually quite quick to do, and so is doubling. So this is quite an efficient strategy we could use.

There are 10 lots of 10 in 100. So to find 10 percent of a number, all we need to do is to divide that number by 10. And what is 3000 divided by 10? The digit shift one place to the right. And we get an answer of 300. So if 10 percent of 3000 equals 300, then 20 percent of 3000 must be worth twice this amount. 300 doubled equals 600. And so we know 20 percent of 3000 equals 600.

We did say there was more than one method we could use. So let’s go through a second strategy that we could use to find the answer. This strategy involves thinking about 20 percent. How many lots of 20 percent are there in 100? One, two, three, four, five. There are five lots of 20 in 100. And so another way of thinking about this is that 20 percent is one-fifth of 100.

So to find 20 percent of 3000, we just need to find one-fifth of 3000 or divide 3000 by five. And if we look carefully at our first method, we know that dividing by 10 and then multiplying by two is the same as dividing by five. And that’s why both methods are going to give us the same answer.

So how many fives are in 3000? Well here, we can use a multiplication fact to help us. We know that 30 divided by five equals six. 3000 is 100 times larger than 30. So there must be 100 times as many fives in it. So the answer must be 600.

As we discussed, percentage questions are always interesting because there’s usually more than one way we could find the answer. Here, we found the answer by first finding 10 percent and then doubling it. And the second strategy was to realise that there are five lots of 20 in 100. So all we had to do was to divide by five and find one-fifth. 20 percent is the same as one-fifth.

So 20 percent of 3000 equals 600.

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