The average age of boys in the class is twice the number of girls in the class. The ratio of boys and girls in the class of 50 is 4: 1. What is the total of the ages (in years) of the boys in the class? [NICL (AO) 2014] |
A) 2000
B) 2500
C) 800
D) 400
E) 500
Correct Answer: C
Solution :
Let total age of boys in the class be x yr. |
Now, number of boys in the class |
\[=\frac{4}{(4+1)}\times 50=\frac{4}{5}\times 50=40\] |
\[\therefore \] Number of girls \[=50-40=10\] |
Now, according to the question, |
\[\frac{{{x}_{1}}+{{x}_{2}}+...+{{x}_{40}}}{40}=2\times 10\] |
\[\Rightarrow \] \[{{x}_{1}}+{{x}_{2}}+...+{{x}_{40}}=800\] |
\[\Rightarrow \] \[x=800\] |
Hence, total age of boys in the class is 800 yr. |
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