The ratio of blue to pink stamps that Gillian had was 5 : 3. The cost of each of the blue stamps was $5 and the cost of each of the pink stamps was $10. Gillian sold 20% of the blue stamps and the total cost of the unsold stamps was $550. How many blue stamps did she have left?
| |
Blue stamps |
Pink stamps |
| Before |
5 u |
3 u |
| Change |
- 1 u |
|
| After |
4 u |
3 u |
Number of blue stamps sold
= 20% x 5 u
=
20100 x 5 u
= 1 u
| |
Blue stamps |
Pink stamps |
Total |
| Number |
4 u |
3 u |
|
| Value |
$5 |
$10 |
|
| Total value |
20 u |
30 u |
$550 |
Total cost of unsold stamps
= 20 u + 30 u
= 50 u
50 u = 550
1 u = 550 ÷ 50 = 11
Number of blue stamps that Gillian had left
= 20 u
= 20 x 11
= 220
Answer(s): 220
