Mary will be 59 years old in 7 years' time. Now, Shiyun's age is 34 of Mary's age. What was Shiyun's age when she was 3 years less than 80% of Mary's age?
| |
Shiyun |
Mary |
Difference |
| Before |
4 p - 3 |
5 p |
1 p + 3 |
| Change 1 |
+ ? |
+ ? |
|
| After 1 (Now) |
3 u |
4 u |
1 u |
| Change 2 |
+ 7 |
+ 7 |
|
| After |
3 u + 7 |
59 |
|
Mary's age in 7 years' time = 4 u + 7
4 u + 7 = 59
4 u = 59 - 7
4 u = 52
1 u = 52 ÷ 4 = 13
Difference between Mary's age and Shiyun's age
= 1 u
= 13
80% =
80100 =
45 Difference in Mary's age and Shiyun's age at first
= 5 p - (4 p - 3)
= 1 p + 3
The difference in age between Mary and Shiyun remains unchanged.
1 p + 3 = 13
1 p = 13 - 3 = 10
Shiyun's age when she was 3 years less than 80% of Mary's age
= 4 p - 3
= 4 x 10 - 3
= 40 - 3
= 37
Answer(s): 37
