Math Is Fun Forum

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Simplest problem in the world and I'm stuck

There are 227 kids in the senior class. Typically 82% of the boys graduate and 87% of the girls. If 175 kids graduate how many of them are boys and how many of them are girls. No answer I get makes sense.

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Simplest problem in the world and I'm stuck

Maybe it's just that the question doesn't have a sensible answer.

The lowest amount of graduates you could get would be if the class was full of boys.
Then the amount of graduates would be 82% of 227, or about 186.

Therefore, 175 is below the lowest possible answer and so no solution can be found.

Less wordily, you could turn the question into some simultaneous equations:
B+G = 227
0.82B + 0.87G = 175

But I'd imagine the answer to that would involve a negative number of girls, so that doesn't work either.

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Why did the vector cross the road?
It wanted to be normal.

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Simplest problem in the world and I'm stuck

Hi mathsyperson;

I got those equations too. The answer has - 222 or so girls, ridiculous!

The lowest amount of graduates you could get would be if the class was full of boys.
Then the amount of graduates would be 82% of 227, or about 186.

Therefore, 175 is below the lowest possible answer and so no solution can be found.

Thanks mathsy, it's the above reasoning I didn't think of. Thanks.

Last edited by bobbym (2009-09-07 06:26:55)

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: Simplest problem in the world and I'm stuck

It said "typically", so I would go with

175 * (82)/(82+87) = 85 boys and hence 90 girls

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"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: Simplest problem in the world and I'm stuck

Yes, that use of 'typically' confuses what the question wants.
If it is a probability-style question though, then we should get told how many boys and girls were in the class to be able to give a correct answer.

For example, if the class was full of boys then 175 boys graduated and no girls did.

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Why did the vector cross the road?
It wanted to be normal.