The ratio of the boys to the girls in a kindergarten was 5 : 3. After 13 boys went home and 11 new girls came, there were 10 more boys than girls in the end. Find the number of pupils in the kindergarten at first.
| |
Boys
(1) |
Girls
(2) |
(3) |
| Before |
5 u |
3 u |
3 u |
| Change |
- 13 |
+ 11 |
+ 11 + 10 = + 21 |
| After |
5 u |
3 u + 11 |
3 u + 21 |
Comparing boys and
girls in the end |
10 more |
|
|
Since the number of boys is 10 more than the number of girls in the end, when we
add 10 to (2) to form (3), the number of boys and girls in the end will be the same.
(1) = (3)
5 u - 13 = 3 u + 21
5 u - 3 u = 21 + 13
2 u = 34
1 u = 34 ÷ 2 = 17
Number of pupils at first
= 5 u + 3 u
= 8 u
= 8 x 17
= 136
Answer(s): 136
