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4.Average
medium
The mean of marks secured by $50$ students in division $A$ of class $X$ is $61,\,25$ students of division $B$ is $57$ and that of $50$ students of division $C$ is $55 .$ What will be the mean of marks of the students of three divisions of Class $X$ ?
A
$57.1$
B
$56.4$
C
$59.2$
D
$57.8$
Solution
Mean of all $3$ class $X=\frac{50 \times 61+25 \times 57+50 \times 55}{50+25+50}$
$=\frac{3050+1425+2750}{125}$
$=57.8$
Std 13
Quantitative Aptitude
