Abi and Sarah had $155. Sarah had $15 more than Abi. Abi spent 4 times as much as Sarah and was left with
25 as much as Sarah. How much did Abi spend?
| |
Make p the same
(1)x5 = (3) |
Abi
(1) |
Sarah
(2) |
Make p the same
(2)x2 = (4) |
Total
|
Comparing Abi
and Sarah at first |
|
|
$15 more |
|
$155 |
| Before |
$350 |
$70 |
$85 |
$170 |
|
| Change |
- 20 u |
- 4 u |
- 1 u |
- 2 u |
|
| After |
10 p |
2 p |
5 p |
10 p |
|
Amount that Abi had at first
= (155 - 15) ÷ 2
= 140 ÷ 2
= $70
Amount that Sarah had at first
= 70 + 15
= $85
70 - 4 u = 2 p --- (1)
85 - 1 u = 5 p --- (2)
Make p the same.
(1)
x 5
350 - 20 u =
10 p --- (3)
(2)
x 2
170 - 2 u =
10 p --- (4)
(4) = (3)
170 - 2 u = 350 - 20 u
20 u - 2 u = 350 - 170
18 u = 180
1 u = 180 ÷ 18 = 10
Amount that Abi spent
= 4 u
= 4 x 10
= $40
Answer(s): $40
