After replacing an old member by a new member, it was found that average age of five members of a cl

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After replacing an old member by a new member, it was found that the average age of five members of a club is the same assit was $3 \,year$ ago. The difference between the ages of the replaced and the new member is ? (in $year$)

A

$2$

B

$4$

C

$8$

D

$15$

Solution

Let the average of $5$ person be $10 \,year.$

Then, sum of their age $=5 \times 10=50$ year

Average age of $5$ member $3$ year ago

$=\frac{50-3 \times 5}{5}+=7$ $year$

So after Adding the new member average become $7 year.$

Difference in the age of old member and New member $=5 \times 10-7 \times 5=15$ $year.$

Standard 13

Quantitative Aptitude

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