The number of girls to the number of boys in Primary 5 Peace was 1 : 4. The number of girls to the number of boys in Primary 5 Gentleness was 4 : 5. Both classes had the same number of girls. When 32 boys from Primary 5 Peace joined Primary 5 Gentleness, the ratio of the number of girls to the number of boys in Primary 5 Peace became 1 : 2. Find the total enrolment of both classes.
Primary 5 Peace |
Primary 5 Gentleness |
Girls |
Boys |
Girls |
Boys |
1x4 |
4x4 |
4x1 |
5x1 |
1x4 |
|
1x4 |
|
4 u |
16 u |
4 u |
5 u |
The number of girls in both classes is the same. Make the number of girls the same. LCM of 1 and 4 is 4.
|
Primary 5 Peace |
Primary 5 Gentleness |
|
Girls |
Boys |
Girls |
Boys |
Before |
4 u |
16 u |
4 u |
5 u |
Change |
|
- 32 |
|
+ 32 |
After |
1x4 = 4 u |
2x4 = 8 u |
4 u |
5 u + 32 |
The number of girls in Primary 5 Peace remains unchanged. Make the number of girls in Primary 5 the same. LCM of 4 and 1 is 4.
Number of boys from Primary 5 Peace that joined Primary 5 Gentleness
= 16 u - 8 u
= 8 u
8 u = 32
1 u = 32 ÷ 8 = 4
Total enrolment of both classes
= 4 u + 16 u + 4 u + 5 u
= 29 u
= 29 x 4
= 116
Answer(s): 116