# Aptitude - Average - Discussion

Discussion Forum : Average - General Questions (Q.No. 2)
2.
A family consists of two grandparents, two parents and three grandchildren. The average age of the grandparents is 67 years, that of the parents is 35 years and that of the grandchildren is 6 years. What is the average age of the family?
 28 4 years 7
 31 5 years 7
 32 1 years 7
None of these
Explanation:
Required average
 = 67 x 2 + 35 x 2 + 6 x 3 2 + 2 + 3
 = 134 + 70 + 18 7
 = 222 7
 = 31 5 years. 7

Video Explanation: https://youtu.be/OXLnoItd0MA

Discussion:
66 comments Page 1 of 7.

Pavithra UH said:   5 years ago
In the question they have already given as average age of grandparents and so on. So why should we multiply that by 2 again? Please, tell me.
(8)

Seenivasan.MG said:   3 years ago
Agree @Pavithra Uh.

Parent means (Mom or Dad) , parents means (both Mom and Dad) , grandparents means (grandma and grandpa (single set)).

Single set = (grandpa and grandma) , Double set = ( (Grandpa and Grandma) , (Grandpa and Grandma) ) likewise.

In question, the Average age of Grandparents (Single set) is 67.

So, we multiply by 2.

Suppose in our question 3 Grandparents means we multiplied by 3.

Correct me, If I am wrong.
(6)

Kavyaa said:   3 years ago
Can't understand anything, please explain me.
(5)

Rjay said:   4 years ago
Why is 31 5/7 is come?
(5)

Abishekbala said:   5 years ago
Grands = 67*2=134,
Mother and Father = 35*2=70,
Child's = 6*3=18.

= 134+70+18/7,
= 222/7,
= 31.71.
(5)

Indhu.p said:   4 years ago
How come 31 5/7 at final? Please explain me.
(3)

Madhav Kulkarn said:   4 years ago
2 GP(Avg age 67) ,
2 P(Avg age 35),
3 Grand CHILD(Avg age 6).
(67*2+35*2+3*6)/7(2+3+2).
(3)

Praju said:   8 years ago
@Neha and @Pratiksha.

Average = sum of the given no /total no.

In the given question you have given the average of 2 grandparents, 2parents and 3 grandchildren. Now you have to calculate the average of all family members.

From the average, we can calculate sum of the numbers as;

Average = sum of the given number/total number.
Sum of the given numbers =avg * total number.

Total number = sum of the given number/avg.

From above data, we can calculate sum of numbers

Avg of 2 grandparents = 67.
Total no grandparents = 2.
Sum of the ages of grandparents = ?

According to formula,
Avg = sum of total no/total no.
Sum of total no = avg * total no.
Sum of total no = 67 * 2 = 134.

Sum of ages of two grandparents is 134 likewise,
Sum of 2 parents is = 35 * 2 = 70.
Sum of three grandchildren is = 6 * 3 = 18.

Now we have to calculate all average of the family.
Total no of family members are 7 i.e. 2 grandparent ,2parents, 3grandchildren
2 + 2 + 3 = .

Avg of total family members = sum of the ages of family members/total no of family members.

As we count sum of ages all family members,
(134 + 70 + 18)/7 = 222/7 = 31.6 = 31 5/7.
(3)

Rutvik said:   12 months ago
How come 5/7? Please explain to me.
(2)

NOGHTI said:   5 years ago
Why can't we consider the chidren as 2 memebers and do the average?
(2)