In a school, average age of students is 6 ,years , and average age of 12 teachers is 40, years. If a

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4.Average

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In a school, the average age of students is $6 \,years$ , and the average age of $12$ teachers is $40\, years.$ If the average age of the combined group of all the teachers and students is $7 \,years$ , then the number of students is?

A

$396$

B

$400$

C

$408$

D

$416$

Solution

Let the number of students $=x$

According to the question

$x \times 6+12 \times 40=(x+12) 7$

$6 x+480=7 x+84 \Rightarrow x=396$

Standard 13

Quantitative Aptitude

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