The ratio of grey to blue stamps that Abi had was 4 : 3. The cost of each of the grey stamps was $2 and the cost of each of the blue stamps was $7. Abi sold 50% of the grey stamps and the total cost of the unsold stamps was $125. How many grey stamps did she have left?
| |
Grey stamps |
Blue stamps |
| Before |
4 u |
3 u |
| Change |
- 2 u |
|
| After |
2 u |
3 u |
Number of grey stamps sold
= 50% x 4 u
=
50100 x 4 u
= 2 u
| |
Grey stamps |
Blue stamps |
Total |
| Number |
2 u |
3 u |
|
| Value |
$2 |
$7 |
|
| Total value |
4 u |
21 u |
$125 |
Total cost of unsold stamps
= 4 u + 21 u
= 25 u
25 u = 125
1 u = 125 ÷ 25 = 5
Number of grey stamps that Abi had left
= 4 u
= 4 x 5
= 20
Answer(s): 20
