The number of boys in the lecture hall was
35 that of the girls. There were 286 more girls than boys. After some girls had left the lecture hall, the number of boys at the lecture hall was thrice the number of the remaining girls. How many girls left the lecture hall?
| |
Girls |
Boys |
Difference |
| Before |
5 u |
3 u |
2 u |
| Change |
- ? |
|
|
| After |
1 u |
3 u |
|
The number of boys at first and in the end remains unchanged.
Number of more girls than boys at first
= 5 u - 3 u
= 2 u
2 u = 286
1 u = 286 ÷ 2 = 143
Number of girls that left
= 5 u - 1 u
= 4 u
= 4 x 143
= 572
Answer(s): 572
