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HELP!- - - -average height

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by tdadic84 » Wed May 27, 2009 2:44 pm
from gmatclub forum...

There are an X number of males and their average height is 77 inches. There are Y femals and their average is 66 inches. If the average height for both males and femals is 70 inches, what us the ratio of X/Y?

please explain how to solve...
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by truplayer256 » Wed May 27, 2009 4:05 pm
If the average height of the x number of males is 77, then their total height must have been 77x.

If the average height of the y number of females is 66, then their total height must have been 66y.

Now take the average of both the males and females heights:

(77x+66y)/x+y=70
77x+66y=70x+70y
7x=4y
7x/4=y
7/4*x/y=1
x/y=4/7
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by p2pg » Thu May 28, 2009 11:31 am
It can be worked like a word problems on mixtures

male female
77 66
70
70-66 : 77-70
4:7 will be the ratio
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by tdadic84 » Thu May 28, 2009 12:33 pm
hey..

can you explain that in greater detail? as well as show the example with a mixture problem....thx!
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by agoyal2 » Fri May 29, 2009 10:19 am
p2pg, I would also like to understand this method. That looked like very quick. What is the mixture problem being referred to? Thanks!
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by sureshbala » Fri May 29, 2009 9:53 pm
Folks you can apply Alligation Technique to finish questions like these very quickly.

Image

This technique can be applied to problems on averages, mixtures, profit & loss as well

Will try to come up with a small tutorial on this soon
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