[Music] in this video we're going to look at how to express one number as a percentage of another number like expressing 15 as a percentage of 25 or expressing 240 grams as a percentage of 320 grams the idea with these is to first of all express them as a fraction and then convert that fraction to a percentage by multiplying it by 100 so for this first question on the left where we need to express 15 as a percentage of 25 we first put it into a fraction so we do the 15 over the 25 and then we can convert that to a percentage by multiplying it by 100 if you can use a calculator then you can just put this straight in and you'll get your answer otherwise you probably want to simplify it down a bit so you could simplify the 15 over 25 to three fifths so that we get three fifths times 100 and then you multiply the three by a hundred to get three hundred over five which is sixty so our final answer is 60 for this next one where we need to express 240 grams as a percentage of 320 grams we do exactly the same thing it doesn't matter that these ones have units we just take the numbers so we do 240 over 320 to express as a fraction then we multiply that by 100 to convert it into a percentage which will give us 75 so our answer is 75 let's have a go at a couple more this first one on the left express 0.3 as a percentage of 1.5 might look a bit tricky because it involves decimals but it works in exactly the same way so we can turn it into a fraction by doing 0.3 over 1.5 and then we just multiply it by 100 to get 20 if you don't have a calculator when you're doing these types of questions it sometimes helps to make the fractions a bit nicer before you multiply them by 100 for example with 0.3 over 1.5 we could multiply the top and bottom by 10 to get rid of the decimals which would give us 3 over 15 and then divide top and bottom by 3 to get 1 over 5 which is much easier to multiply by 100 because it becomes 100 over 5 which is 20. for this second one express 1.2 kilos as a percentage of 800 grams there are two things that make it a bit different the first is that the two numbers have different units kilograms and grams so we first need to make them both the same and it's probably easier to convert the 1.2 kilos into grams which would do by multiplying it by 1000 to get 1200 grams the other difference is that 1200 is bigger than 800. so when we express it as a fraction by doing 1200 grams over 800 grams we get a top heavy or improper fraction because our numerator is bigger than our denominator this doesn't really make any difference but it doesn't mean that our final answer once we've multiplied it by 100 should be bigger than 100 which it is because this simplifies to 150 so just remember that if your numerator is bigger than your denominator then your percentage will be bigger than 100 now sometimes in your exams you might get a question that's buried within a scenario for example the price of a new car falls by 4 000 pounds in the first year if the original price of the car was 32 000 pounds what percentage did its value decrease by so this is basically the same as all of the other questions that we've been doing this video the only difference is that we need to pick the important numbers out for ourselves so this time we're basically trying to find 4 000 pounds as a percentage of 32 000 pounds so we're gonna have to do 4 000 divided by 32 000 and then times that by 100 to get 12.5 percent as our answer anyway that's everything for this video so i hope it all made sense and you found it useful if you did then please do tell your friends about us and we'll see you again soon cheers