Mr. Joe’s family consists of six people-himself, his wife and their four children. It is known that the average age of the family immediately after the birth of the first, second, third and fourth child was 16, 15, 16 and 15 years respectively. Find the age of the Mr. Joe’s eldest son if the present average age of the entire family is 16 years. (a) 8 yrs.                      (b) 12 yrs.                 (c) 15 yrs.                 (d) 16 yrs.

Question ID - 50912 :- Mr. Joe’s family consists of six people-himself, his wife and their four children. It is known that the average age of the family immediately after the birth of the first, second, third and fourth child was 16, 15, 16 and 15 years respectively. Find the age of the Mr. Joe’s eldest son if the present average age of the entire family is 16 years. (a) 8 yrs.                      (b) 12 yrs.                 (c) 15 yrs.                 (d) 16 yrs.

3537

When the first child was born, the total age of all the family members = years.

When the second child was born, the total age of all the family members =

years.

By the time the second child was born, each one of the 3 family members had grown by =  years.

Hence, the age of the eldest son when the second child was born = 4 years.

When the third child was born, the total age of all the family members =

years.

By the time the third child was born, each one of the 4 family members had grown by =  years.

Hence, the age of the eldest son when the third child was born = 4+5 =9 years.

When the fourth child was born, the total age of all the family members =

years.

By the time the fourth child was born, each one of the 5 family members had grown by =  years.

Hence, the age of the eldest son when the fourth child was born = 9+2

=11 years.

At present, the total age of all the 6 family members =

96 years.

By now, each one of the 6 members have grown by 1 year.

Hence, the present age of the eldest son =  = 12 years.

Next Question :

Total expenses of a boarding house are partly fixed and partly varying linearly with the number of boarders. The average expense per boarder is Rs. 700 when there are 25 boarder and Rs. 600 when there are 50 boarders. What is the average expense per boarder when there are 100 boarders?

(a) Rs. 540                               (b) Rs. 550                          (c) Rs. 570                  (d) Rs. 580