The ratio of grey to red stamps that Yoko had was 5 : 4. The cost of each of the grey stamps was $4 and the cost of each of the red stamps was $6. Yoko sold 20% of the grey stamps and the total cost of the unsold stamps was $160. How many grey stamps did she have left?
| |
Grey stamps |
Red stamps |
| Before |
5 u |
4 u |
| Change |
- 1 u |
|
| After |
4 u |
4 u |
Number of grey stamps sold
= 20% x 5 u
=
20100 x 5 u
= 1 u
| |
Grey stamps |
Red stamps |
Total |
| Number |
4 u |
4 u |
|
| Value |
$4 |
$6 |
|
| Total value |
16 u |
24 u |
$160 |
Total cost of unsold stamps
= 16 u + 24 u
= 40 u
40 u = 160
1 u = 160 ÷ 40 = 4
Number of grey stamps that Yoko had left
= 16 u
= 16 x 4
= 64
Answer(s): 64
