The ratio of the girls to the boys in a school was 7 : 3. After 13 girls went home and 14 new boys came, there were 5 more girls than boys in the end. Find the number of pupils in the school in the end.
| |
Girls
(1) |
Boys
(2) |
(3) |
| Before |
7 u |
3 u |
3 u |
| Change |
- 13 |
+ 14 |
+ 14 + 5 = + 19 |
| After |
7 u |
3 u + 14 |
3 u + 19 |
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 - 13 = 3 u + 19
7 u - 3 u = 19 + 13
4 u = 32
1 u = 32 ÷ 4 = 8
Number of pupils in the end
= 7 u + 3 u - 13 + 14
= 10 u + 1
= 10 x 8 + 1
= 80 + 1
= 81
Answer(s): 81
