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I have a simple question in probability which I solved in one way (I'm not $100\%$ sure It's right and I'm looking for another (more simple) way to solve it).

The ratio between the red balls and the yellow balls is $5:7$.

If there are $60$ balls overall, how much are red balls and how much are yellow balls?

My solution:

Add $5+7$ you get $12$.

Now $60/12 = 5$.

now $5*5 =$ number of red balls

and $7*5 = $ number of yellow balls.

is it correct?

Do you have another way, a simple way to solve it?

Thanks in advance, Guy

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6  
Absolutely correct. And a best approach, there is no need to drag in algebra. –  André Nicolas Oct 28 '12 at 19:46
1  
Without knowing distribution, yes. –  Inquest Oct 28 '12 at 19:46
4  
Your solution is correct but this is not a probability question as it is completely deterministic. No probability is involved. –  Barry Oct 28 '12 at 19:51
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2 Answers 2

up vote 1 down vote accepted

You set up the following equations:

$$\frac{\rm red}{\rm yellow}=\frac{5}{7}$$

We are given that $\rm red+yellow=60$, therefore, we have $\rm red=\frac{5}{7}\rm yellow$, or $\frac{12}{7} \rm yellow=60$. Therefore, $\rm yellow=35$ and $\rm red=25$ using simple algebra.

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Not sure this is simpler :-) –  Julian Kuelshammer Oct 28 '12 at 20:38
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therefore,yellow has=35 and red=25 using algebra

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This is simply reiterating the last line of Justin Stevens' answer. –  robjohn Apr 6 '13 at 16:47
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