When Yoko was 39 years old, her son was 2 times her daughter's age. Yoko would be twice her son's age when her daughter was 21 years old. How old would Yoko be when her daughter was 8 years old?
|
Yoko |
Son |
Daughter |
Before |
39 |
2 u |
1 u |
Change |
+ ? |
+ ? |
+ ? |
After |
2 p |
1 p |
21 |
The difference in the ages between Yoko and her son remains unchanged.
Difference in Yoko's and her son's ages at first
39 - 2 u = 2 p - 1 p
39 - 2 u =
1 p --- (1)
The difference in the ages between her son and her daughter remains unchanged.
Difference in her son's and her daughter's ages at first
2 u - 1 u = 1 p - 21
1 u + 21 =
1 p --- (2)
Make p the same.
(1) = (2)
39 - 2 u = 1 u + 21
1 u + 2 u = 39 - 21
3 u = 18
1 u = 18 ÷ 3 = 6
Age difference between Yoko and her daughter
= 39 - 1 u
= 39 - 6
= 33
Yoko's age when her daughter was 8 years old
= 33 + 8
= 41
Answer(s): 41