Winnie and Mary have some money. If Winnie spends $6, she will have
25 as much money as Mary. If Mary spends $7, Winnie will have
57 as much money as Mary. How much money does Mary have?
| |
Case 1 |
Case 2 |
| |
Winnie |
Mary |
Winnie |
Mary |
| Before |
2 u + $6 |
5 u |
5 p |
7 p + $7 |
| Change |
- $6 |
|
|
- $7 |
| After |
2 u |
5 u |
5 p |
7 p |
The amount that Winnie has at first in Case 1 and Case 2 is the same.
2 u + 6 = 5 p
2 u = 5 p - 6 --- (1)
The amount that Mary has at first in Case 1 and Case 2 is the same.
5 u = 7 p + 7 --- (2)
Make u the same.
(1)
x 510 u = 25 p - 30 --- (3)
(2)
x 210 u = 14 p + 14 --- (4)
(3) = (4)
25 p - 30 = 14 p + 14
25 p - 14 p = 30 + 14
11 p = 44
1 p = 44 ÷ 11 = 4
Amount that Mary has
= 7 p + 7
= 7 x 4 + 7
= 28 + 7
= $35
Answer(s): $35
