At first, there were 400 more boys than girls at the museum. By 1 p.m., a total of 278 boys and girls left the museum. There were as many boys as girls who left the museum. In the end, there were 3 times as many boys as girls who remained behind. How many boys were at the museum at first?
| |
Boys |
Girls |
Difference |
| Before |
3 u + 139 |
1 u + 139 |
400 |
| Change |
- 139 |
- 139 |
|
| 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 = 400
1 u = 400 ÷ 2 = 200
Number of boys in the end
= 3 u
= 3 x 200
= 600
Number of boys that left
= 278 ÷ 2
= 139
Number of boys at first
= 600 + 139
= 739
Answer(s): 739
