HELP!- - - -average height

[tdadic84]

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...

[truplayer256]

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

[p2pg]

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

[tdadic84]

hey..

can you explain that in greater detail? as well as show the example with a mixture problem....thx!

[agoyal2]

p2pg, I would also like to understand this method. That looked like very quick. What is the mixture problem being referred to? Thanks!

[sureshbala]

Folks you can apply Alligation Technique to finish questions like these very quickly.



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