The average age of six brothers is 15 years. If their father is also included, the average is increased by 7 years. Find the age of the father(in years).
Answer & explanation
Correct answer: option 3
Average age of the family = $\frac{sum\;of \;ages\;of\;all\;members}{6}$
⇒ 15 = $\frac{sum\;of \;ages\;of\;all\;members}{6}$
⇒ Sum of ages of all members = 15 x 6 = 90
Now, if the father's age(say, $x$ years) is added,
Sum of ages of all members = 90 + $x$
Then, average becomes (15 + 7) 22
⇒ $\frac{90+x}{7}$ = 22
⇒ 90 + $x$ = 154
⇒ $x$ = 64