Percent

[neeti2711]

Forty percent of the rats included in an experiment were male rats. If some of the rats died during 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

[Anurag@Gurome]

Forty percent of the rats included in an experiment were male rats. If some of the rats died during 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

Algebraic Method:

Total no. of rats = R
No. of rats that died = N

No. of male rats = 40% of R = 0.4R
Death rate of male rats = 0.3N/0.4R
Death rate of female rats = 0.7N/0.6R

Therefore, ratio of the death rate among the male rats to the death rate among the female rats = (0.3N/0.4R)/(0.7N/0.6R) = 18/28 = [spoiler]9/14[/spoiler]

The correct answer is A.

[puneetkhurana2000]

Died Not Died Total
Male 0.3x 40
Female 0.7x 60
Total x 100

Let us assume the total number of deaths is x, by given information male deaths is 0.3x and female will be x-0.3x = 0.7x.

There is no need to fill up second columns as we need death rate i.e. (0.3x/40)/(0.7x/60) = 9/14

Hope this helps.

[puneetkhurana2000]

Sorry, the table got messed up...the numbers 40, 60 and 100 should be in last column under Total.

And 0.3x, 0.7x and x should be in first column under Died.

Second column is blank as explained in my previous post.

Hope this makes sense!!

[GMATGuruNY]

Forty percent of the rats included in an experiment were male rats. If some of the rats died during 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

Let the total number of rats = 100.
Male rats = .4(100) = 40.
Thus, female rats = 100-40 = 60.

Let the total number of deaths = 10.
Male deaths = .3(10) = 3.
Thus, female deaths = 10-3 = 7.

Male death rate = (male deaths)/(total males) = 3/40.
Female death rate = (female deaths)/(total females) = 7/60.
Male death rate / female death rate = (3/40) / (7/60) = 3/40 * 60/7 = 9/14.

The correct answer is A.