At first, there were 408 more girls than boys at the concert hall. By 1 p.m., a total of 276 girls and boys left the concert hall. There were as many girls as boys who left the concert hall. In the end, there were 4 times as many girls as boys who remained behind. How many girls were at the concert hall at first?
|
Girls |
Boys |
Difference |
Before |
4 u + 138 |
1 u + 138 |
408 |
Change |
- 138 |
- 138 |
|
After |
4 u |
1 u |
3 u |
Since there was the same number of boys and girls that left, the difference between the number of boys and girls remains unchanged.
3 u = 408
1 u = 408 ÷ 3 = 136
Number of girls in the end
= 4 u
= 4 x 136
= 544
Number of girls that left
= 276 ÷ 2
= 138
Number of girls at first
= 544 + 138
= 682
Answer(s): 682