In a hall,
18 of the pupils wore cardigans. After 100 pupils who wore cardigans entered the hall, the percentage of pupils who wore cardigans increased to 75%. How many pupils in the hall did not wear cardigans?
| |
Wore cardigans |
Did not wear cardigans |
| Before |
1x1 =
1 u |
7x1 =
7 u |
| Change |
+ 100 |
|
| After |
3x7 =
21 u |
1x7 =
7 u |
75% =
75100 =
34The number of pupils who did not wear cardigans remains unchanged. LCM of 7 and 1 is 7.
Number of pupils who wore cardigans and left
= 21 u - 1 u
= 20 u
20 u = 100
1 u = 100 ÷ 20 = 5
Number of pupils who did not wear cardigans
= 7 u
= 7 x 5
= 35
Answer(s): 35
