Question

In a class, the average age of 30 boys is 14 years and the average of 20 girls is 10 years. What is the average age of the whole class?

Answer 1

(30×14)+(20×10)=620
620/50=12.5 ans

Answer 2

$We \:know \:that ,$

$\boxed { \pink { Average = \frac{ Sum \:of \: the \: observations }{Number \:of \: observations }} }$

$i ) Average \: age \: of \: boys = 14$

$Number \:of \:boys = 30$

$\therefore Sum \:of \: ages \:of \: boys \\= Average \times number \:of \:boys \\= 14 \times 30 \\= 420$

$ii) Average \: age \: of \: girls = 10 \: years$

$Number \:of \: girls = 20$

$\therefore Sum \:of \: ages \:of \: girls \\= Average \times number \:of \:girls \\= 10\times 20 \\= 200$

$Now , Total \: number \:of \: students\\ = </p><p>30 + 20 \\= 50$

$Total \: sum \: of \:ages \: of \: students \\= 420 + 200 \\=620$

$\red { Average \:age \:whole \:class } \\= \frac{ 620}{50} \\= 12.4 \: years$

Therefore.,

$\red { Average \:age \:whole \:class }\green {= 12.4 \: years}$

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