Tiffany and Irene have some money. If Tiffany spends $6, she will have
25 as much money as Irene. If Irene spends $4, Tiffany will have
78 as much money as Irene. How much money does Irene have?
| |
Case 1 |
Case 2 |
| |
Tiffany |
Irene |
Tiffany |
Irene |
| Before |
2 u + $6 |
5 u |
7 p |
8 p + $4 |
| Change |
- $6 |
|
|
- $4 |
| After |
2 u |
5 u |
7 p |
8 p |
The amount that Tiffany has at first in Case 1 and Case 2 is the same.
2 u + 6 = 7 p
2 u = 7 p - 6 --- (1)
The amount that Irene has at first in Case 1 and Case 2 is the same.
5 u = 8 p + 4 --- (2)
Make u the same.
(1)
x 510 u = 35 p - 30 --- (3)
(2)
x 210 u = 16 p + 8 --- (4)
(3) = (4)
35 p - 30 = 16 p + 8
35 p - 16 p = 30 + 8
19 p = 38
1 p = 38 ÷ 19 = 2
Amount that Irene has
= 8 p + 4
= 8 x 2 + 4
= 16 + 4
= $20
Answer(s): $20
