Seven minutes ago, 70% of the students in a hall were girls. 66 students left the hall. As a result, the number of girls decreased by 20% and the number of boys decreased by 80%. How many students are in the hall at first?
| |
Girls |
Boys |
Total |
| Before |
10 u |
3 u |
13 u |
| Change |
- 2 u |
- 2.4 u |
- 4.4 u |
| After |
8 u |
0.6 u |
8.6 u |
70% =
70100 =
710Number of girls who left the hall
= 20% x 10 u
=
20100 x 10 u
= 2 u
Number of boys who left the hall
= 80% x 3 u
=
80100 x 3 u
= 2.4 u
Total number of students who left the hall
= 2 u + 2.4 u
= 4.4 u
4.4 u = 66
1 u = 66 ÷ 4.4 = 15
Number of students in the hall at first
= 10 u + 3 u
= 13 u
= 13 x 15
= 195
Answer(s): 195
