Video: GCSE Mathematics Foundation Tier Pack 2 • Paper 1 • Question 21

GCSE Mathematics Foundation Tier Pack 2 • Paper 1 • Question 21

02:46

Video Transcript

On Monday and Tuesday, Helen picks some blackberries. On Monday, she picks 50 blackberries. On Tuesday, she picks 60 blackberries. Work out the percentage increase in the number of blackberries she picks from Monday to Tuesday.

So the first thing we need to do is actually find out the difference in blackberries she picks between Monday and Tuesday. And to do that, what we do is we subtract 50 from 60, which gives us a result of 10. So we know that actually she picked 10 more blackberries on Tuesday than she did on Monday.

But now, what we need to do is actually work out the percentage increase in the number of blackberries she picks from Monday to Tuesday. So we worked out the difference, but how we’re gonna use this to work out the increase in percentage? Well, to help us actually calculate the percentage increase, we have this formula. And that tells us that the percentage increase is equal to the difference divided by the original multiplied by 100.

Well, then, if we take a look at the information we’ve got. We’ve got a difference of 10 because we’ve calculated that. And then, the original number of blackberries was actually 50 because that’s what she picked on a Monday. So therefore, we can say that the percentage increase is gonna be equal to 10 over 50 multiplied by 100 because that’s our difference over our original multiplied by 100.

Well, now, we can actually calculate this. What I can actually do is to split it up because we’ve got 10 over 50 multiplied by 100. But what we can actually do is do 100 divided by 50 which is two, which will give us 10 multiplied by two because we had the 10 from the original numerator and then multiplied it by the two because we had 100 divided by 50 which give us two which gives us an answer of 20. So that means there’s a 20 percent increase in the number of blackberries picked from Monday to Tuesday. Okay, great, so we’ve solved the problem.

I’m just gonna show you an alternative way to have actually calculated that. Well, alternatively, we’d have 10 over 50 multiplied by 100. So therefore, we could use to divide the numerator and denominator by 10. So we get one over five or a fifth multiplied by 100. Well, a fifth of 100, so a fifth multiplied by 100, is the same as dividing 100 by five. If we do 100 divided by five, we get 20. And that’s because one way of thinking about it is if you have 10 divided by five would be two then add on a zero, so therefore again we get 20 percent.

So therefore, we can definitely say that the increase in the number of blackberries that Helen picked from Monday to Tuesday is 20 percent.

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