Eleven minutes ago, 80% of the students in a hall were boys. 54 students left the hall. As a result, the number of boys decreased by 40% and the number of girls decreased by 70%. How many students are in the hall at first?
| |
Boys |
Girls |
Total |
| Before |
5 u |
1 u |
6 u |
| Change |
- 2 u |
- 0.7 u |
- 2.7 u |
| After |
3 u |
0.3 u |
3.3 u |
80% =
80100 =
45Number of boys who left the hall
= 40% x 5 u
=
40100 x 5 u
= 2 u
Number of girls who left the hall
= 70% x 1 u
=
70100 x 1 u
= 0.7 u
Total number of students who left the hall
= 2 u + 0.7 u
= 2.7 u
2.7 u = 54
1 u = 54 ÷ 2.7 = 20
Number of students in the hall at first
= 5 u + 1 u
= 6 u
= 6 x 20
= 120
Answer(s): 120
