Average age of 5 members is 21 ,years. If age of youngest member be 5 ,years, find out average age o

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The average age of $5$ members is $21 \,years.$ If the age of the youngest member be $5 \,years,$ find out the average age of the family at the birth of the youngest member.(in $years$)

A

$24$

B

$25$

C

$20$

D

$28$

Solution

Total age of $5$ members $=21 \times 5=105$ years.

Total age of $4$ members at the birth of the youngest member, that is, $5$ years ago $=105-(5 \times 5)=80$ years

Before the birth of the youngest member, the family consisted of only $4$ members.

Average age of $4$ members $5$ years ago

$=\frac{80}{4}=20$ years.

Standard 13

Quantitative Aptitude

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