Mary will be 88 years old in 10 years' time. Now, Emma's age is 56 of Mary's age. What was Emma's age when she was 4 years less than 90% of Mary's age?
| |
Emma |
Mary |
Difference |
| Before |
9 p - 4 |
10 p |
1 p + 4 |
| Change 1 |
+ ? |
+ ? |
|
| After 1 (Now) |
5 u |
6 u |
1 u |
| Change 2 |
+ 10 |
+ 10 |
|
| After |
5 u + 10 |
88 |
|
Mary's age in 10 years' time = 6 u + 10
6 u + 10 = 88
6 u = 88 - 10
6 u = 78
1 u = 78 ÷ 6 = 13
Difference between Mary's age and Emma's age
= 1 u
= 13
90% =
90100 =
910 Difference in Mary's age and Emma's age at first
= 10 p - (9 p - 4)
= 1 p + 4
The difference in age between Mary and Emma remains unchanged.
1 p + 4 = 13
1 p = 13 - 4 = 9
Emma's age when she was 4 years less than 90% of Mary's age
= 9 p - 4
= 9 x 9 - 4
= 81 - 4
= 77
Answer(s): 77
