The ratio of the boys to the girls in a school was 5 : 2. After 19 boys went home and 30 new girls came, there were 5 more boys than girls in the end. Find the number of pupils in the school in the end.
| |
Boys
(1) |
Girls
(2) |
(3) |
| Before |
5 u |
2 u |
2 u |
| Change |
- 19 |
+ 30 |
+ 30 + 5 = + 35 |
| After |
5 u |
2 u + 30 |
2 u + 35 |
Comparing boys and
girls in the end |
5 more |
|
|
Since the number of boys is 5 more than the number of girls in the end, when we
add 5 to (2) to form (3), the number of boys and girls in the end will be the same.
(1) = (3)
5 u - 19 = 2 u + 35
5 u - 2 u = 35 + 19
3 u = 54
1 u = 54 ÷ 3 = 18
Number of pupils in the end
= 5 u + 2 u - 19 + 30
= 7 u + 11
= 7 x 18 + 11
= 126 + 11
= 137
Answer(s): 137
