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4.Average
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$16$ children are to be divided into two groups $A$ and $B$ of $10$ and $6$ children. The average percent marks obtained by the children of group $A$ is $75$ and the average per cent marks of all the $16$ children is $76 .$ What is the average per cent marks of children of group $B$ ?
A
$77 \frac{1}{3}$
B
$78 \frac{1}{3}$
C
$77 \frac{2}{3}$
D
$78 \frac{2}{3}$
Solution
Group $A$ average $=75$
Group $( A + B )$ average $=76$
Required average $=\frac{16 \times 76-10 \times 75}{6}$
$=\frac{760+456-750}{6}=\frac{466}{6}$
$=77 \frac{4}{6}=77 \frac{2}{3} \%$
Standard 13
Quantitative Aptitude
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