On a shelf, there were 70 skirts and cardigans. David spilt soy milk on the shelf and stained 50% of the cardigans and 20% of the skirts. If 53 skirts and cardigans were still clean, how many clean cardigans were there?
| |
Skirts |
Cardigans |
Total |
| Stained |
1 u |
1 p |
17 |
| Clean |
4 u |
1 p |
53 |
| Total |
5 u |
2 p |
70 |
50% =
50100 =
12 20% =
20100 =
15 Number of stained clothes
= 70 - 53
= 17
4 u + 1 p = 53
1 p = 53 - 4 u --- (1)
1 u + 1 p = 17
1 p = 17 - 1 u --- (2)
(2) - (1)
17 - 1 u = 53 - 4 u
4 u - 1 u = 53 - 17
3 u = 36
1 u = 36 ÷ 3 = 12
Number of clean cardigans is the same as the number of stained cardigans.
Number of clean cardigans
= 17 - 1 u
= 17 - 12
= 5
Answer(s): 5
