The ratio of black to white stamps that Barbara had was 5 : 2. The cost of each of the black stamps was $5 and the cost of each of the white stamps was $7. Barbara sold 20% of the black stamps and the total cost of the unsold stamps was $238. How many white stamps did she have left?
| |
Black stamps |
White stamps |
| Before |
5 u |
2 u |
| Change |
- 1 u |
|
| After |
4 u |
2 u |
Number of black stamps sold
= 20% x 5 u
=
20100 x 5 u
= 1 u
| |
Black stamps |
White stamps |
Total |
| Number |
4 u |
2 u |
|
| Value |
$5 |
$7 |
|
| Total value |
20 u |
14 u |
$238 |
Total cost of unsold stamps
= 20 u + 14 u
= 34 u
34 u = 238
1 u = 238 ÷ 34 = 7
Number of white stamps that Barbara had left
= 14 u
= 14 x 7
= 98
Answer(s): 98
