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1000 PS section 8- Q-20

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1000 PS section 8- Q-20

by ash_maverick » Tue May 26, 2009 3:00 am
Forty percent of the rats included in an experiment were male rats. If some of the rats died during the experiment and 30 percent of the rats that died were male rats, what was the ratio of the death rate among the male rats to the death rate among the female rats?

(A) 9/14
(B) 3/4
(C) 9/11
(D) 6/7
(E) 7/8

Please explain.
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by bluementor » Tue May 26, 2009 3:17 am
Lets say total number rats used in the experiment = T

No. of male rats = 0.4T
No. of female rats = 0.6T

No. of rats that died = D

No. of male rats that died = 0.3D
No. of female rats that died = 0.7D

male death rate = 0.3D/0.4T
female death rate = 0.7D/0.6T

so ratio of death rates = (0.3D/0.4T)/(0.7D/0.6T) = (0.3x0.6)/(0.4x0.7) = 18/28 = 9/14

Choose A.

-BM-
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