The ratio of the boys to the girls in a kindergarten was 5 : 2. After 15 boys went home and 30 new girls came, there were 15 more boys than girls in the end. Find the number of children in the kindergarten in the end.
| |
Boys
(1) |
Girls
(2) |
(3) |
| Before |
5 u |
2 u |
2 u |
| Change |
- 15 |
+ 30 |
+ 30 + 15 = + 45 |
| After |
5 u |
2 u + 30 |
2 u + 45 |
Comparing boys and
girls in the end |
15 more |
|
|
Since the number of boys is 15 more than the number of girls in the end, when we
add 15 to (2) to form (3), the number of boys and girls in the end will be the same.
(1) = (3)
5 u - 15 = 2 u + 45
5 u - 2 u = 45 + 15
3 u = 60
1 u = 60 ÷ 3 = 20
Number of children in the end
= 5 u + 2 u - 15 + 30
= 7 u + 15
= 7 x 20 + 15
= 140 + 15
= 155
Answer(s): 155
