The number of boys in the lecture hall was
49 that of the girls. There were 170 more girls than boys. After some girls had left the lecture hall, the number of boys at the lecture hall was four times the number of the remaining girls. How many girls left the lecture hall?
|
Girls |
Boys |
Difference |
Before |
9 u |
4 u |
5 u |
Change |
- ? |
|
|
After |
1 u |
4 u |
|
The number of boys at first and in the end remains unchanged.
Number of more girls than boys at first
= 9 u - 4 u
= 5 u
5 u = 170
1 u = 170 ÷ 5 = 34
Number of girls that left
= 9 u - 1 u
= 8 u
= 8 x 34
= 272
Answer(s): 272