Fifteen minutes ago, 60% of the students in a parade square were boys. 70 students left the parade square. As a result, the number of boys decreased by 40% and the number of girls decreased by 75%. How many students are in the parade square at first?
| |
Boys |
Girls |
Total |
| Before |
5 u |
2 u |
7 u |
| Change |
- 2 u |
- 1.5 u |
- 3.5 u |
| After |
3 u |
0.5 u |
3.5 u |
60% =
60100 =
35Number of boys who left the parade square
= 40% x 5 u
=
40100 x 5 u
= 2 u
Number of girls who left the parade square
= 75% x 2 u
=
75100 x 2 u
= 1.5 u
Total number of students who left the parade square
= 2 u + 1.5 u
= 3.5 u
3.5 u = 70
1 u = 70 ÷ 3.5 = 20
Number of students in the parade square at first
= 5 u + 2 u
= 7 u
= 7 x 20
= 140
Answer(s): 140
