The ratio of the girls to the boys in a kindergarten was 5 : 2. After 20 girls went home and 17 new boys came, there were 5 more girls than boys in the end. Find the number of students in the kindergarten at first.
| |
Girls
(1) |
Boys
(2) |
(3) |
| Before |
5 u |
2 u |
2 u |
| Change |
- 20 |
+ 17 |
+ 17 + 5 = + 22 |
| After |
5 u |
2 u + 17 |
2 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)
5 u - 20 = 2 u + 22
5 u - 2 u = 22 + 20
3 u = 42
1 u = 42 ÷ 3 = 14
Number of students at first
= 5 u + 2 u
= 7 u
= 7 x 14
= 98
Answer(s): 98
