Aptitude - Problems on Ages - Discussion

11. 

The present ages of three persons in proportions 4 : 7 : 9. Eight years ago, the sum of their ages was 56. Find their present ages (in years).

[A]. 8, 20, 28
[B]. 16, 28, 36
[C]. 20, 35, 45
[D]. None of these

Answer: Option B

Explanation:

Let their present ages be 4x, 7x and 9x years respectively.

Then, (4x - 8) + (7x - 8) + (9x - 8) = 56

20x = 80

x = 4.

Their present ages are 4x = 16 years, 7x = 28 years and 9x = 36 years respectively.


Neha said: (Jul 3, 2010)  
How 20x comes?

Faruk said: (Aug 23, 2010)  
4x+7x+9x = 56+8+8+8

20x = 80

is it simplified.

Affrin said: (Dec 16, 2010)  
(4x-8)+(7x-8)+(9x-8) = 56 --->(1)
Now add all the "x" values and "numerical number" separetely in eqn (1) then we get:
4x+7x+9x = 20x
(-8)+(-8)+(-8) = -24
20x-24 = 56
20x = 56+24
20x = 80
x = 80/20
x = 4
so,for calculating the current age we are substituting x=4 in (4x:7x:9x)= we get the ratio as 16:28:36

Habib said: (Feb 20, 2011)  
For such ques......jst simply look at the options !!!!

Try subtracting 8 frm B...and den add u get 56 !!!!

Hit and Trial...saves time !!!! :)

Jagadeesh said: (Mar 4, 2011)  
4x+7x+9x=80
20x=80
x=4
then we get answer

Rahima said: (Mar 23, 2011)  
Just add all the x terms and numerical terms seperately.

Shiva said: (Mar 24, 2011)  
Shiva

(4x-8)+(7x-8)+(9x-8)= 56
Remove the braces.
4x-8+7x-8+9x-8 =56
Now seperate variables and numeric terms.
4x+7x+9x=56+8+8+8
20x=80
x=4.
njoy.

Payal said: (May 21, 2011)  
Habib method was good

Ganesh said: (Jul 15, 2011)  
Nice and easy method.

Pragathi said: (Aug 8, 2011)  
Actually ago means past time so we have to add it's my doubt some times you will add some times you subtract please clarify it.

Sumit said: (Aug 19, 2011)  
@Habib method is good.

Swetha said: (Sep 1, 2011)  
Habib method is good:-).

Chenchu said: (Sep 12, 2011)  
Can't understand habib's method of subracting 8 from b.

Ankit Rathore said: (Sep 18, 2011)  
Good explanation

Vissu said: (Sep 27, 2011)  
Sum of there ages is 56 before 8 years then after 8 years it must be 64.

Virendra Rajput said: (Nov 22, 2011)  
Just look option which are having given ratio 4:7:9

A and D are ruled out then check 2"nd condition.

Madhu said: (Nov 30, 2011)  
Ago means we can subtract that given value, after means add that value.

Adinarayana said: (Dec 5, 2011)  
Faruk explained detail but I didn't understand, how is it came 8, how did you take the 56+8+8+8.

Ronak said: (Dec 28, 2012)  
The total of ratios is 20 (4+7+9).
The total of ages will become 56 + (8x3) = 56+24 = 80.

Now 20 x 4 = 80,
So the multiple is 4. So the common multiple is 4 for all.
Now we get present ages of all.

4x4 = 16.
7x4 = 28.
9x4 = 36.

Anu said: (Jan 6, 2013)  
When should we use (+) and (-) symbols under this section means problems based on age.

Vijay Anand said: (Aug 23, 2013)  
@Anu.

AGO means(-).

SINCE, AFTER means(+).

Sam said: (Jun 3, 2014)  
Search for the common multiplier.
Here 4 matches exactly i.e.,

4*4 = 16.
4*7 = 28.
4*9 = 36.

Naveen Kumar said: (Jul 21, 2014)  
x(4+7+9) = 56+8+8+8.
Then we got x = 4.

For further answer each x term multiplied by 4.

Vinutha said: (Aug 19, 2014)  
Simple method:

4*4 = 16.
7*4 = 28.
9*4 = 36.

Djdave said: (Jan 4, 2015)  
f1:f2:f3 = 4:7:9.

f1 + f2 + f3 - 24 = 56.
f1 + f2 + f3 = 80.

f1 = 4 / 20 * 80 = 16.
f2 = 7/20 * 80 = 28.
f3 = 9/20 * 80 = 36.

Roshni said: (Jan 17, 2015)  
It is a ratio of three values then why plus is coming?

Sanju said: (Aug 17, 2015)  
4x-8+7x-8+9x-8=56 x=4 then 4x=16 is present ages.

Ravi said: (Sep 25, 2015)  
Why they minuses with 8?

Yunus said: (Nov 28, 2015)  
It is simple that eight years ago 56 and now 3 persons*8 years each = 24 years.

So 56+24 = 80 now we check options the sum of 80 is 16+28+36 = 80 is option B answer.

Karthika.L said: (Mar 1, 2016)  
Please explain in easy way?

Ramya said: (Sep 28, 2016)  
It is simple method.

He has given present ages of persons mentioned that 8 years ago, then we can take as;
(4x - 8) + (7x - 8) + (9x - 8) = 56.

Lavanya said: (Mar 2, 2017)  
8 years ago sum of their age is 56,
Present sum of their age is 80
Total parts of the ratio is 4+7+9 = 20
So, 80/20=4
4 * 4 ,7 * 4, 9 * 4 = 16, 28, 36.

Pawan Kumar said: (Aug 4, 2017)  
How to add 8?

Jon said: (Aug 7, 2017)  
I didn't understand.
First of all, from where 80 came.
Secondly, how do we know that we must plus, 4x-8 and 7x-8 how come there is + in between. Isn't it 8 years ago. Then why plus?

Please, someone, explain in very simple manner.

Tanweer said: (Sep 4, 2018)  
8 year ago total age 56.

Now 8x3=24+56=80 answer is B.

Tirth Patel said: (Sep 23, 2018)  
4 + 7 + 9 = 20x.

Eight years ago* three persons(8*3)=24.
Sum of their ages was= 56.
24+56=80x.
80/20=4.

Then 4:7:9 multiply by 4.
(4*4)=16,
(7*4)=28,
(9*4)=36.
The Answer is 16, 28, 36.

Krishan said: (Aug 18, 2019)  
8 years ago the sum of ages was 56.

At present, the sum of age will be 3*8+56 = 80.

Post your comments here:

Name *:

Email   : (optional)

» Your comments will be displayed only after manual approval.