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 4 of 6.
Malu said:
1 decade ago
Ratio of present age of mother and son is 5:2.
After 8 years ratio becomes 2:1.
So x = 8*(2-1)/5-4 = 8.
Mothers age is 8*5 = 40.
After 8 years ratio becomes 2:1.
So x = 8*(2-1)/5-4 = 8.
Mothers age is 8*5 = 40.
Javid Mir said:
1 decade ago
Hii.
Let present age of man = x and that of mother = y.
Then, x = 2/5y....equation....(1).
After 8 years, x+8 = 1/2(y+8).
x+8 = 1/2*y+1/2*8.
x+8 = y/2 + 4.
Substituting the value of x in equation....(1) we get,
2/5y+8 = y/2+4.
2y+40/5 = y+8/2.
On cross multiplication we get.
4y+80 = 5y+40.
4y-5y = 40-80.
-y = -40 or y = 40.
Let present age of man = x and that of mother = y.
Then, x = 2/5y....equation....(1).
After 8 years, x+8 = 1/2(y+8).
x+8 = 1/2*y+1/2*8.
x+8 = y/2 + 4.
Substituting the value of x in equation....(1) we get,
2/5y+8 = y/2+4.
2y+40/5 = y+8/2.
On cross multiplication we get.
4y+80 = 5y+40.
4y-5y = 40-80.
-y = -40 or y = 40.
(1)
Aparna mohan said:
1 decade ago
How 59(x+8) came?
Sumit said:
1 decade ago
Person mother.
2 5.
1 2 (8 year hence).
Then mother's present age is.
M = (5*8*1)/(5*1) - (2*2).
M = 40.
2 5.
1 2 (8 year hence).
Then mother's present age is.
M = (5*8*1)/(5*1) - (2*2).
M = 40.
Kiran said:
1 decade ago
Second step how wrote by first line?
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?
Shivani said:
1 decade ago
In question they have asked present age of mother, But 40 is after 8 years old. Shouldn't it be 40-8-32?
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.
Leena said:
1 decade ago
Can anybody explain me?
(2x+40)/5 = (x+8)/2.
4x + 80 = 5x + 40.
(2x+40)/5 = (x+8)/2.
4x + 80 = 5x + 40.
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?
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