The ratio of the boys to the girls in a school was 7 : 4. After 25 boys went home and 20 new girls came, there were 6 more boys than girls in the end. Find the number of students in the school at first.
|
Boys (1) |
Girls (2) |
(3) |
Before |
7 u |
4 u |
4 u |
Change |
- 25 |
+ 20 |
+ 20 + 6 = + 26 |
After |
7 u |
4 u + 20 |
4 u + 26 |
Comparing boys and girls in the end |
6 more |
|
|
Since the number of boys is 6 more than the number of girls in the end, when we
add 6 to (2) to form (3), the number of boys and girls in the end will be the same.
(1) = (3)
7 u - 25 = 4 u + 26
7 u - 4 u = 26 + 25
3 u = 51
1 u = 51 ÷ 3 = 17
Number of students at first
= 7 u + 4 u
= 11 u
= 11 x 17
= 187
Answer(s): 187