The number of boys in the lecture hall was
57 that of the girls. There were 260 more girls than boys. After some girls had left the lecture hall, the number of boys at the lecture hall was five times the number of the remaining girls. How many girls left the lecture hall?
|
Girls |
Boys |
Difference |
Before |
7 u |
5 u |
2 u |
Change |
- ? |
|
|
After |
1 u |
5 u |
|
The number of boys at first and in the end remains unchanged.
Number of more girls than boys at first
= 7 u - 5 u
= 2 u
2 u = 260
1 u = 260 ÷ 2 = 130
Number of girls that left
= 7 u - 1 u
= 6 u
= 6 x 130
= 780
Answer(s): 780