On a shelf, there were 78 sweaters and skirts. Zeph spilt soy milk on the shelf and stained 50% of the skirts and 20% of the sweaters. If 57 sweaters and skirts were still clean, how many clean skirts were there?
| |
Sweaters |
Skirts |
Total |
| Stained |
1 u |
1 p |
21 |
| Clean |
4 u |
1 p |
57 |
| Total |
5 u |
2 p |
78 |
50% =
50100 =
12 20% =
20100 =
15 Number of stained clothes
= 78 - 57
= 21
4 u + 1 p = 57
1 p = 57 - 4 u --- (1)
1 u + 1 p = 21
1 p = 21 - 1 u --- (2)
(2) - (1)
21 - 1 u = 57 - 4 u
4 u - 1 u = 57 - 21
3 u = 36
1 u = 36 ÷ 3 = 12
Number of clean skirts is the same as the number of stained skirts.
Number of clean skirts
= 21 - 1 u
= 21 - 12
= 9
Answer(s): 9
