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
Answer: Option
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 2 of 7.

Bhuwaneshwaran said:   6 years ago
How taking grandchildren has 3? They haven't mentioned count of grandchildren.

Grace said:   6 years ago
@Ravisinh Mori, @Banita and @Ankur Mishra.

We must emphasise on the term grandparent. When we are talking about only one person (either mother or father of a grandchild) it is termed as a grandparent.

While we are talking about two people (both mother and father of a grandchild) it is termed as grandparents. Hence 2 is mentioned just to clarify that the question is talking about 2 people.

Because they have used it as a plural with plural.
(1 person=grandparent & 2 person=grandparents).

Spvn said:   7 years ago
Thanks @Rupinderjit.

Ravisinh mori said:   7 years ago
How total person 7 in a family?

Total person is 11 because 2 grandparents = 4person, 2 parents = 4person, 3children so total is 11 instead of 7.

Jatin007 said:   7 years ago
No @Arvind.

The number of people is 7 so we have to divide with 7. Read the question carefully. You will find the answer.

Arvind said:   7 years ago
Can we add all the avgs and divide by 3?

The avg of grandparents, grandchildren and parents are given
67 + 35 + 6/3 = 36.

Am I right?

Shivu said:   7 years ago
Friends, how we write 222/7 into 31*5/7? Please tell me.

Shivu said:   7 years ago
Thank you for all the explanation of the solution.

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)

Neha said:   8 years ago
How can you say that grandchildren are three?


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