At first, there were 436 more boys than girls at the zoo. By 3 p.m., a total of 258 boys and girls left the zoo. There were as many boys as girls who left the zoo. In the end, there were 3 times as many boys as girls who remained behind. How many boys were at the zoo at first?
|
Boys |
Girls |
Difference |
Before |
3 u + 129 |
1 u + 129 |
436 |
Change |
- 129 |
- 129 |
|
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 = 436
1 u = 436 ÷ 2 = 218
Number of boys in the end
= 3 u
= 3 x 218
= 654
Number of boys that left
= 258 ÷ 2
= 129
Number of boys at first
= 654 + 129
= 783
Answer(s): 783