+600 1. It takes 3 pumps 15 hours to fill a swimming pool. How many pumps would it take to fill the pool in 9 hours?
2. It takes 200 tiles to tile a room when each tile covers 36cm2. If I use tiles which covers 25cm2, how many tiles would I use?
+118687 Hi Eloise :)
I think it is probably easiest to use a unitary method for these.
1. It takes 3 pumps 15 hours to fill a swimming pool. How many pumps would it take to fill the pool in 9 hours?
3 pumps take 15 hours
so 1 pump must take 3 times longer than that. 15*3=45hours
1pump takes 45 hours
Now 45 divided by 5 = 9 hous which is the number you want.
If you are going to do it 5 times faster then it will take 5 times more pumps 1*5=5 pumps
So
it will take 5 pumps to fill the pool in 9 hours
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2. It takes 200 tiles to tile a room when each tile covers 36cm2. If I use tiles which covers 25cm2, how many tiles would I use?
200 tiles when each is 36cm^2
If the tiles are only 1cm^2 then the tiles are 36 times smaller and you will need 36 times 200 tiles 36*200 = 7200 tiles (if they are really little just 1cm^2 each)
But the ones we want are 25cm^2 each, that is 25 times bigger than the really little ones. They are a 25 times bigger so we will need to divide the number of tiles by 25
7200 divided by 25 = 288 tiles.
So if the tiles cover 25cm^2 each, you will need 288 tiles.
You had best buy some extra ones because there will be some cut peices that you will not want to use ;)
