Seventeen minutes ago, 60% of the students in a canteen were girls. 20 students left the canteen. As a result, the number of girls decreased by 20% and the number of boys decreased by 75%. How many students are in the canteen at first?
| |
Girls |
Boys |
Total |
| Before |
5 u |
2 u |
7 u |
| Change |
- 1 u |
- 1.5 u |
- 2.5 u |
| After |
4 u |
0.5 u |
4.5 u |
60% =
60100 =
35Number of girls who left the canteen
= 20% x 5 u
=
20100 x 5 u
= 1 u
Number of boys who left the canteen
= 75% x 2 u
=
75100 x 2 u
= 1.5 u
Total number of students who left the canteen
= 1 u + 1.5 u
= 2.5 u
2.5 u = 20
1 u = 20 ÷ 2.5 = 8
Number of students in the canteen at first
= 5 u + 2 u
= 7 u
= 7 x 8
= 56
Answer(s): 56
