Aptitude - Problems on Ages - Discussion
Discussion Forum : Problems on Ages - General Questions (Q.No. 13)
13.
A person's present age is two-fifth of the age of his mother. After 8 years, he will be one-half of the age of his mother. How old is the mother at present?
Answer: Option
Explanation:
Let the mother's present age be x years.
| Then, the person's present age = |  |
2 | x |  |
years. |
| 5 |
 |
|
2 | x + 8 | |
= | 1 | (x + 8) |
| 5 | 2 |
2(2x + 40) = 5(x + 8)
x = 40.
Discussion:
59 comments Page 2 of 6.
Nag Repala said:
6 years ago
If we suppose mothers age as 40 then son's age will be 16years according to 2/5th part. Then after 8years son's age will be 24years and mothers age is. 48years. This is also half of the mother. Then this is also correct only, right? Please correct me, if I am wrong.
(3)
Tim said:
9 years ago
But here, it did not specify whether the mothers age also adjusted. I think this is how you should have phrased this part. "After 8 years, he will be one-half of the age of his mother THEN". Notice the word then, it makes it much clearer.
Sam said:
1 decade ago
As far as I can see in the third step they have taken the LCM on Left hand side but didn't do that on the right hand side. Just wondering if I am right. And if that's the case why didn't they do the same on RHS (right hand side) ?
Mrs pallavi said:
1 decade ago
Let the person age x, mother age y.
x=2/5*y............condn(1)
(x+8)=1/2(y+8).....condn(2)
from 1
5x-2y=0.........(a)
from 2
2x-y=-8 ..........(b)
from a & b
we get x=16 & y=40
Answer is 40.
x=2/5*y............condn(1)
(x+8)=1/2(y+8).....condn(2)
from 1
5x-2y=0.........(a)
from 2
2x-y=-8 ..........(b)
from a & b
we get x=16 & y=40
Answer is 40.
Vijitha said:
1 decade ago
Can any one explain me - one half means 3/2 or 1/2 - if exactly one-half means 3/2 means- why they taken it as 1/2 while solving - please explain me about the difference of both?
Uzma said:
1 decade ago
2x/5+8/1 = 1/2(x+8).
(here we are going to cross multiply 5*8 = 40).
2x = 40/5 = 1/2(x+8).
2x = 40/5 = 1/2(x+8).
4x+80 = 5x+40.
Then x = 80-40.
= 40.
Hope you got it.
(here we are going to cross multiply 5*8 = 40).
2x = 40/5 = 1/2(x+8).
2x = 40/5 = 1/2(x+8).
4x+80 = 5x+40.
Then x = 80-40.
= 40.
Hope you got it.
Cynthia said:
1 decade ago
Please I need explanation on solving this equation:
2/5x+8 = 1/2(x+8).
Are we not meant to cross multiply. I don't understand how you came about the 40?
2/5x+8 = 1/2(x+8).
Are we not meant to cross multiply. I don't understand how you came about the 40?
Kishan said:
9 years ago
Let the mother present age = x.
Man's age = 2x/5.
x + 8 = 1/2 (2x/8 * 5),
x + 8 = 4x/16 * 5,
x + 8 = 4x/16 * 5,
x + 8 = 4x + 80/5,
5x + 40 = 4x + 80,
x = 40.
Man's age = 2x/5.
x + 8 = 1/2 (2x/8 * 5),
x + 8 = 4x/16 * 5,
x + 8 = 4x/16 * 5,
x + 8 = 4x + 80/5,
5x + 40 = 4x + 80,
x = 40.
Vivek said:
1 decade ago
One-half is 3/2 and not 1/2 and the x denotes the current age! so by what they have solved, 40 is right!! but one half is 3/2 and definitely not 1/2!
Arjun bhaskar purekar said:
3 years ago
Suppose, the mother's age is 100 years and person's age has two-fifth of his mother then two-fifth of 100 is 40 years.
2/5 * 100 = 40.
2/5 * 100 = 40.
(16)
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