At first, there were 390 more boys than girls at the concert hall. By 4 p.m., a total of 262 boys and girls left the concert hall. There were as many boys as girls who left the concert hall. In the end, there were 3 times as many boys as girls who remained behind. How many boys were at the concert hall at first?
|
Boys |
Girls |
Difference |
Before |
3 u + 131 |
1 u + 131 |
390 |
Change |
- 131 |
- 131 |
|
After |
3 u |
1 u |
2 u |
Since there was the same number of girls and boys that left, the difference between the number of girls and boys remains unchanged.
2 u = 390
1 u = 390 ÷ 2 = 195
Number of boys in the end
= 3 u
= 3 x 195
= 585
Number of boys that left
= 262 ÷ 2
= 131
Number of boys at first
= 585 + 131
= 716
Answer(s): 716