In a hall,
310 of the pupils wore vests. After 75 pupils who wore vests entered the hall, the percentage of pupils who wore vests increased to 80%. How many pupils in the hall did not wear vests?
|
Wore vests |
Did not wear vests |
Before |
3x1 = 3 u |
7x1 = 7 u |
Change |
+ 75 |
|
After |
4x7 = 28 u |
1x7 = 7 u |
80% =
80100 =
45The number of pupils who did not wear vests remains unchanged. LCM of 7 and 1 is 7.
Number of pupils who wore vests and left
= 28 u - 3 u
= 25 u
25 u = 75
1 u = 75 ÷ 25 = 3
Number of pupils who did not wear vests
= 7 u
= 7 x 3
= 21
Answer(s): 21