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Sixty percent of the rats included in a particular experiment were female rats. If some of the rats died during the experiment and 30% of rats died were male, what was the ratio of the death rate among the male rats to the death rate among the female rats?
1. 3 : 4
2. 9 : 14
3. 9 : 16
4. 6 : 7

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Correct Answer - Option 2 : 9 : 14

Given:

Female rat in particular experiment = 60%

Male rats in particular experiment = 40%

Female rats died in experiment = 70%

Male rats died in experiment = 30% 

Calculation:

Let the number of rats be x 

The number of female rats  = 60% of x = 0.6x 

Number of male rats = 40% of x = 0.4x

Let the number of rats that died be y 

The number of female rats died = 70% of y = 0.7y

Number of male rats died =  30% of y = 0.3y

Death rate of male rats = \(\frac{0.3y}{0.4x}\) = \(\frac{3y}{4x}\)      ----(I)

Death rate of female rats = \(\frac{0.7y}{0.6x}\) = \(\frac{7y}{6x}\)      ----(II)

Equating (I) and (II)  

⇒ \(\frac{3y}{4x}\) = \(\frac{7y}{6x}\)  = 18xy : 28xy

∴ The ratio of the death rate of male to female rats is 9 : 14            

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