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4.Average
medium
There are two groups $A$ and $B$ of a class, consisting of $42$ and $28$ students, respectively. If the average weight of group $A$ is $25 \,kg$ and that of group $B$ is $40 \,kg ,$ find the average weight of the whole class.
A
$69$
B
$31$
C
$70$
D
$30$
Solution
Required average weight $=\frac{42 \times 25+28 \times 40}{42+28}$
$=\frac{1050+1120}{70}=\frac{2170}{70}=31 \,kg$
Standard 13
Quantitative Aptitude