The ratio of purple to gold stamps that Zara had was 5 : 4. The cost of each of the purple stamps was $1 and the cost of each of the gold stamps was $3. Zara sold 40% of the purple stamps and the total cost of the unsold stamps was $120. How many gold stamps did she have left?
| |
Purple stamps |
Gold stamps |
| Before |
5 u |
4 u |
| Change |
- 2 u |
|
| After |
3 u |
4 u |
Number of purple stamps sold
= 40% x 5 u
=
40100 x 5 u
= 2 u
| |
Purple stamps |
Gold stamps |
Total |
| Number |
3 u |
4 u |
|
| Value |
$1 |
$3 |
|
| Total value |
3 u |
12 u |
$120 |
Total cost of unsold stamps
= 3 u + 12 u
= 15 u
15 u = 120
1 u = 120 ÷ 15 = 8
Number of gold stamps that Zara had left
= 12 u
= 12 x 8
= 96
Answer(s): 96
