The ratio of the girls to the boys in a kindergarten was 7 : 4. After 17 girls went home and 17 new boys came, there were 5 more girls than boys in the end. Find the number of children in the kindergarten at first.
| |
Girls
(1) |
Boys
(2) |
(3) |
| Before |
7 u |
4 u |
4 u |
| Change |
- 17 |
+ 17 |
+ 17 + 5 = + 22 |
| After |
7 u |
4 u + 17 |
4 u + 22 |
Comparing girls and
boys in the end |
5 more |
|
|
Since the number of girls is 5 more than the number of boys in the end, when we
add 5 to (2) to form (3), the number of girls and boys in the end will be the same.
(1) = (3)
7 u - 17 = 4 u + 22
7 u - 4 u = 22 + 17
3 u = 39
1 u = 39 ÷ 3 = 13
Number of children at first
= 7 u + 4 u
= 11 u
= 11 x 13
= 143
Answer(s): 143
