Average height of students of a class of 20 is 105, cm . If ten more students of average height of 1

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The average height of the students of a class of $20$ is $105\, cm$. If ten more students of average height of $120 \,cm$ join this class, the average height of the class will become (in $cm$)

A

$115.7$

B

$115$

C

$110$

D

$112.5$

Solution

Average height of $20$ students in a class $=105 cm$.

After joining $10$ students of average height $120 cm ,$ average height of students of the class

$=\frac{20 \times 105+10 \times 120}{30}=2 \times 35+10 \times 4=70+40=110 \,cm$

Standard 13

Quantitative Aptitude

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