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4.Average

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The average age of a group of $15$ students is $10 \,years.$ When $5$ more students joined the group, the average got increased by $1\, year.$ The age of the new student is (in $years$)

A

$18$

B

$16$

C

$14$

D

$12$

Solution

Old average of $15$ atudenta $=10$ years.

$5$ more students joined the group.

New average $=10+1=11$ years.

Let Age of new student= $x$ years

$\frac{15 \times 10+5 \times x}{20}=11$

$5 x=20 \times 11-15 \times 10=70$

$x=\frac{70}{5}=14$ years

Std 13

Quantitative Aptitude

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