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4.Average

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The average age of $8$ members of a group is $40 \,years.$ The age of $1$ member is $55\, years.$ After his retirement a new member comes in his place of age $39 .$ What is the effect of his retirement on the average age of group ?

A

$2$

B

$0$

C

$3$

D

$5$

Solution

Total age of $8$ members $=8 \times 40=320$ $years.$

Total age after replacement of $1$ member $=320-55+39=304$ $years.$

New average $=\frac{304}{8}=38$ $years$

Hence average decreased by $2 \,years.$

Std 13

Quantitative Aptitude

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