Aptitude - Average - Discussion

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?

[A].
28  4 years
7
[B].
31  5 years
7
[C].
32  1 years
7
[D]. None of these

Answer: Option B

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


Anonymous said: (Oct 7, 2011)  
In the answer how 5 comes can someone tell me.

Sanjana said: (Oct 13, 2011)  
It's remainder.

While we perform 222/7 quotent will be 31 nd remainder would be 5.

Moreshwar Pidadi said: (Nov 21, 2011)  
No because in question it is givven an avarage an no. Of person so answer seams to be correct an each age is being taken out.

Eric said: (Jan 24, 2012)  
When already the avg ages of grandparents, parents and children are given! why they have been multiplied by 2, 2 and 3 respectively?

Steffi said: (Feb 27, 2012)  
In the answer how 6x3 came?

Swati said: (Mar 6, 2012)  
There are 2 grandparents of 67yrs (67*2)
2 parents of 35yrs (35*2)
3 grandchildren of 6yrs (6*3)
average = sum of total ages/no.of persons
67 x 2 + 35 x 2 + 6 x 3 divided by 2 + 2 + 3
=31 5/7
Hope that explains if not plz correct me.

Sarath said: (Mar 13, 2012)  
Thank you swathi.

Ankur Mishra said: (May 20, 2012)  
As you are mentioning in question that 2 grandparents are there means 4 peoples (Because grandparent consists of 2 Members)and same as in parents 2 parents means 4 person again. Then i hope here total members are 11.
Hope it is correct if not please correct me

Rupinderjit said: (May 30, 2012)  
(grandpa+granny)/2=67=134
(ma+pa)/2=35=70
(rinku+minku+chinku)/3=6=18

Now average age is(total age of all members/no of members) = 222/7(grandpa,granny,ma,pa,chinku,minku,rinku)

Hope it'll help you

Banita said: (Aug 21, 2012)  
I have the same concern of 11 memebers as parents includes 2 people, which Ankur mishra explained, please help me out!

Iqra said: (Nov 29, 2012)  
Numbers of children is not mentioned here?

Naina said: (Dec 13, 2012)  
Exactly no.of children is not given then how 3 is taken?

H.R said: (Dec 15, 2012)  
They are mention three grandchildren observe the problem again.

Krishna said: (Apr 18, 2013)  
@Eric: The numbers are not equal, grandparents are 2, parents are also 2 but children are 3. so don't take avg figure.

Grand parents avg age of 2 = 67, but 2 people are there so 67*2.
Parents avg age of 2 = 35, 2 people are two so 35+35 or 35*2.
Children are 3 avg age = 6, people are three so 6+6+6 or 6*3.

If in the question if he said children also two then you can take avg directly.

Naani said: (Jul 17, 2013)  
It's so simple.

A = S/N.

S = A*N.

Total Sum = (2*67)+(2*35)+(3*6) = 222.

Number of people in that family = 2+2+3 = 7.

So Average=Total Sum/Num of people.

A = 222/7.

A = 31 5/7. ((7*31)+5 =222/7).

Yatin said: (Sep 30, 2013)  
Consider, Average age of grandparents is given i.e. avg = 67.

Also number of grandparents = 2.

By definition of average.

Average = total observations of all objects/total no of objects.

Let sum of individual ages of grandparents = X.

In this case,

Substituting in above formula,

67 = X/2.

Hence, X = 67x2.

And rest is average concept.

Thanks :).

Rabindra Gouda said: (Nov 13, 2013)  
Total member of the family is 11. How it 7?

Rashmi Poddar said: (Dec 2, 2013)  
Parents are grandparents means 2 people then 2 grandparents are parents means 4 nd 4 people respectively then how its here only 2 people for grandparents and parents?

Nilin said: (Feb 15, 2014)  
But I wanted to know how it comes from 222/7 to 31 5/7?

Navi said: (Apr 10, 2014)  
Sorry I wanted also to know how it comes from 222/7 to 31 5/7?

Surendra said: (Jun 28, 2014)  
We know that answer is 222/7.

Verify the options: all options consist the denominator 7.
We have the numerator 222.

In 222 units place is 2.
For 31 5/7 we have to multiply 31 and 7 and to the result we have to add 5.

In 31x7 the units place is 7(since 1x7=7).
To that 7 we will add 5, the result is 12 in which the units place is 2 which matches with the units place of 222.

For all other options the units place is not 2.

Faizan said: (Jul 4, 2014)  
Now see, let denote grand parent by gp,

The average age of grandparents is given as 67,
Which means (gp1+gp2)/2 is equal to 67.

Similarly,
(p1+p2)/2 is equal to 35.

Similarly,
(gc1+gc2)/2 is equal to 6.

We are required to find,
(gp1+gp2+p1+p2+gc1+gc2)/7 is ?

So we found numerator by this way as:
67*2+35*2+6*2 = numerator.

Stalin said: (Sep 3, 2014)  
In this problem mention two grandparents (i.e. two grandfather and two grand mother) then how it come total member in this family is 7?

I think total member is 11 explain me.

Mkr said: (Sep 9, 2014)  
Question says A family, so I think in a family there will be one grandpa and granny and also there will be only one mom and one dad. So answer is right.

Negi said: (Sep 16, 2014)  
How do you know they have 3 children. Confused?

Anuj said: (Oct 7, 2014)  
I wanted to know how it comes from 222/7 to 31 5/7?

Tamilazhagan said: (Oct 19, 2014)  
I think total members are 11. Because parent = mother and father. So 2 parents is equal for 2 mother and 2 father. Then grand parents are also 2 grand mother and 2 grand father. So total members are 11.

Swe said: (Nov 1, 2014)  
@Tamilazhagan

Yes you are correct that is the correct process and answer is none of these.

Ali said: (Nov 15, 2014)  
That's current value is not better for this question.

Siva Subramania Krishnan S said: (Nov 18, 2014)  
I have a question see they have given average age of parents is 35 but they didn't which parents, so grandparents are parents of the existing two parents rite.

Therefore there are totally 4 parents and the total age of parents should be (35*4) not (35*2) and the answer is none of the above.

My answer is 40 2/7.

Dhivya R said: (Dec 31, 2014)  
Your calculation wrong @Mr.Siva.

Because the given question is 2 grandparents, 2 parents, 3 grandchildren.

Average age of grandparents is 67. So age of two grandparents is 67*2 = 134. Average age of parents is 35. So age of two parents is 35*2 = 70. Average age of three grandchildren is 6. So age of three grandchildren is 6*3 = 18.

Average = Sum of observation/Number of observation.

Average = 134+70+18/2+2+3.

Average = 222/7.

We convert ordinary fraction into mixed fraction.

So finally we get average = 31 5/7.

Kraminka said: (Jan 28, 2015)  
Average = Sum of total ages/No of person.

Average = 67*2+35*2+6*3/2+2+3.

= 134+70+18/7 = 222/7 = 31 5/7.

Shubham Sanware said: (Apr 10, 2015)  
Can you explain 31 5/7 with formula ?

Adithya said: (May 6, 2015)  
@Shubham Sanware.

It is the mixed fraction of 222/7. When you divide 222 with 7 we get 31 as quotient and remainder 5.

Mixed fraction = quotient remainder/divisor.

So, its 31 5/7.

Masterneeji said: (Jun 7, 2015)  
@Tamilazhagan.

Parent means either mummy or daddy.

Parents means couple so we (67*2+35*2+6*3)/2+2+3 = 222/7 = 31 5/7.

Ramesh said: (Jun 13, 2015)  
How the 5 is coming? Can anyone explain what is remainder?

Er. Ashish Yadav said: (Jul 17, 2015)  
Required average = 67 x 2 + 35 x 2 + 6 x 3.
-----------------------
2 + 2 + 3
= 134 + 70 + 18
---------------
7
= 222
-----
7
= 31 5 years.
-
7

Divide:

7)222(31
- 21
-------
12
- 7
-------
5
-------
so that is right it like 31 5
--------------------------
7

Changlu said: (Jul 24, 2015)  
How comes 5/7 I got 31.7142?

Faizal Hussain said: (Sep 5, 2015)  
Please explain, why for parents also your multiplying by 2 and for two grandparents also multiplying by 2. Why can't we consider like this.

For parents means = Father and mother, hence its multiplied by 2.

For 2 grandparents means = Father's father, father's mother, mother'father, mothers mother, hence it should be 4.

Please some one reply am I right or wrong, if no please explain.

Divya Arora said: (Sep 25, 2015)  
Can someone crack such problems with some other approach, shortcut maybe?

Susant said: (Oct 10, 2015)  
Why 222 would became 315? Can someone please explain me?

Sridevi said: (Dec 16, 2015)  
Family = Two grand parents = 2*67 = 134, two parents = 2*35 = 70, three grand children = 3*6 = 18.

After started in 134+70+18. Total members: 222/7 = 31.5/7.

Harini said: (Dec 18, 2015)  
It's a wrong method already average of ages were given how can we count them as 7 members.

Siddhant said: (Apr 2, 2016)  
In question they mention that 2 parents and 2 grandparents, parents mean father and mother both, then why 67 and 35 are multiplied by 2, why not 4. Because there are 2 parents.

Kamal Jeet said: (May 27, 2016)  
According to Question : 2 Grandparents mean two members (Grandfather and Grandmother) Not mean to say (2 Grandfather or 2 Grandmother)!

And same follow as two Parents (Dad and Mom).

At Last 2 + 2 + 3 = 7.

I hope you understood.

Pratiksha said: (Aug 11, 2016)  
Can someone tell me that 31.5 is the write answer?

Neha said: (Aug 12, 2016)  
How can you say that grandchildren are three?

Praju said: (Sep 12, 2016)  
@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.

Shivu said: (Oct 31, 2016)  
Thank you for all the explanation of the solution.

Shivu said: (Oct 31, 2016)  
Friends, how we write 222/7 into 31*5/7? Please tell me.

Arvind said: (Dec 2, 2016)  
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?

Jatin007 said: (Feb 13, 2017)  
No @Arvind.

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

Ravisinh Mori said: (Mar 31, 2017)  
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.

Spvn said: (Jun 21, 2017)  
Thanks @Rupinderjit.

Grace said: (Jul 19, 2018)  
@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).

Bhuwaneshwaran said: (Aug 21, 2018)  
How taking grandchildren has 3? They haven't mentioned count of grandchildren.

Shubham J said: (Jan 31, 2019)  
Thanks for the answer @Rupinderjit.

Pavithra Uh said: (May 25, 2019)  
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.

Abishekbala said: (Jul 6, 2019)  
Grands = 67*2=134,
Mother and Father = 35*2=70,
Child's = 6*3=18.

= 134+70+18/7,
= 222/7,
= 31.71.

Noghti said: (Jul 27, 2019)  
Why can't we consider the chidren as 2 memebers and do the average?

Post your comments here:

Name *:

Email   : (optional)

» Your comments will be displayed only after manual approval.