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4.Average
medium
The average of the test scores of a class of $'m'$ students is $70$ and that of $'n'$ students is $91.$ When the scores of both the classes are combined, the average is $80 .$ What is $n / m$ ?
A
$\frac{11}{10}$
B
$\frac{13}{10}$
C
$\frac{10}{13}$
D
$\frac{10}{11}$
Solution
Total score of a class of $m$ students $=70 \times m$
Total score of a class of $n$ students $=91 \times n$
$70 m + 91 n =( m + n ) 80 \quad 70 m +91 n =80 m +80 n$
$11 n =10 m \Rightarrow \frac{ n }{ m }=\frac{10}{11}$
Standard 13
Quantitative Aptitude
