Betty and Irene had $152. Irene had $8 more than Betty. Betty spent 3 times as much as Irene and was left with
35 as much as Irene. How much did Betty spend?
| |
Make p the same
(1)x5 = (3) |
Betty
(1) |
Irene
(2) |
Make p the same
(2)x3 = (4) |
Total
|
Comparing Betty
and Irene at first |
|
|
$8 more |
|
$152 |
| Before |
$360 |
$72 |
$80 |
$240 |
|
| Change |
- 15 u |
- 3 u |
- 1 u |
- 3 u |
|
| After |
15 p |
3 p |
5 p |
15 p |
|
Amount that Betty had at first
= (152 - 8) ÷ 2
= 144 ÷ 2
= $72
Amount that Irene had at first
= 72 + 8
= $80
72 - 3 u = 3 p --- (1)
80 - 1 u = 5 p --- (2)
Make p the same.
(1)
x 5
360 - 15 u =
15 p --- (3)
(2)
x 3
240 - 3 u =
15 p --- (4)
(4) = (3)
240 - 3 u = 360 - 15 u
15 u - 3 u = 360 - 240
12 u = 120
1 u = 120 ÷ 12 = 10
Amount that Betty spent
= 3 u
= 3 x 10
= $30
Answer(s): $30
