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 Forum Index >  Test Paper Related >  Primary 4 Matters
 Another P4 Maths question - please help
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By: tangara (offline)  Wednesday, July 20 2011 @ 10:03 PM CDT (Read 1082 times)  
tangara

hi forum members,

I would like to seek advise on how to do the following question below:-

At a school event, 1/4 of the people were boys.
4/5 of the girls and 3/5of the boys didn't know how to swim.

If there were 150 swimmers at the event, how many people were there altogether?

Thanks.

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Registered: 07/31/10
Posts: 26

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By: YTNg (offline)  Thursday, July 21 2011 @ 01:48 AM CDT  
YTNg

hi, let me try to solve this question.

Since 1/4 of the people were boys, fraction of girls must be 3/4.

4/5 of girls don't know how to swim, means 1/5 of the girls know how to swim
1/5 x 3/4 = 3/20

3/5 of boys don't know how to swim, means 2/5 of the boys know how to swim
2/5 x 1/4 = 2/20

Total number of people is 20 units
5 units know how to swim
5 units = 150
1 unit = 150/5 = 30

Total number of people will be 20 units x 30 = 600.

Please correct me if I am wrong. Wink


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By: tangara (offline)  Thursday, July 28 2011 @ 11:19 PM CDT  
tangara

Quote by: YTNg

hi, let me try to solve this question.

Since 1/4 of the people were boys, fraction of girls must be 3/4.

4/5 of girls don't know how to swim, means 1/5 of the girls know how to swim
1/5 x 3/4 = 3/20

3/5 of boys don't know how to swim, means 2/5 of the boys know how to swim
2/5 x 1/4 = 2/20

Total number of people is 20 units
5 units know how to swim
5 units = 150
1 unit = 150/5 = 30

Total number of people will be 20 units x 30 = 600.

Please correct me if I am wrong. Wink




That's correct. Tks.

I was having mind-block...trying out the modelling method...and just can't get it right.

Your solution just open up my eyes.

Tks.

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Registered: 07/31/10
Posts: 26

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