Maths GCSE Revision – Lesson #2
This lesson from the ‘Number’ section of GCSE Maths is all about Multiples and Factors (transcript below video).
Now we’re going to have a quick look at multiples and factors. The multiples of a number are just it’s times table. For example, the multiples of 3 are 3, 6, 9, 12, 15, 18 and so on. This can go on forever, and it is the same for any number.
The factors of a number are the numbers that divide in to it. For example, if we’re looking at the factors of 12, the best way to find them is to think of pairs of numbers that multiply together to give you 12. We could have, 1 x 12, 2 x 6 and 3 x 4. These are all the pairs of numbers that multiply together to give you 12. So if you were going to list all of the factors of 12 you would just list these numbers individually, which would give us 1, 2, 3, 4, 6 and 12.
We have an exam question here which is all about multiples. It says ‘Use the numbers from this list to answer the question’, and we have a list of numbers there. Part ‘a’ says, write down all the multiples of 5. You can see there is 5, 25 and 30, as the multiples of 5.
For part ‘b’ we need to write down all the factors of 100. These are all the numbers that we could divide 100 by, and get a whole number. If we go through from left to right, we could divide 100 by 5, but 12 and 17 do not go in to 100. 25 does, as it goes in 4 times. 28, 30, 42 and 49 do not go in to 100, so we are just left with 5 and 25.
Part ‘c’, write down a square number. 5, 12 and 17 are not square numbers. 25 is, as it is 5 x 5, and 49 is a square number too as it is 7 x 7. We only need to choose one, so let’s go with 25.
In part ‘d’ we need to write down three numbers that have a sum of 60, which means they add up to give us 60. If you look at the three numbers we chose in part ‘a’, 5, 25 and 30, and you add them up, you end up with 60. So that’s perfect, we can use these numbers for our answer, as 5 + 25 + 30 = 60.
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