The ratio of gold to grey stamps that Tina had was 5 : 3. The cost of each of the gold stamps was $5 and the cost of each of the grey stamps was $10. Tina sold 20% of the gold stamps and the total cost of the unsold stamps was $600. How many grey stamps did she have left?
| |
Gold stamps |
Grey stamps |
| Before |
5 u |
3 u |
| Change |
- 1 u |
|
| After |
4 u |
3 u |
Number of gold stamps sold
= 20% x 5 u
=
20100 x 5 u
= 1 u
| |
Gold stamps |
Grey stamps |
Total |
| Number |
4 u |
3 u |
|
| Value |
$5 |
$10 |
|
| Total value |
20 u |
30 u |
$600 |
Total cost of unsold stamps
= 20 u + 30 u
= 50 u
50 u = 600
1 u = 600 ÷ 50 = 12
Number of grey stamps that Tina had left
= 30 u
= 30 x 12
= 360
Answer(s): 360
