The number of girls to the number of boys in Primary 4 Peace was 1 : 4. The number of girls to the number of boys in Primary 4 Goodness was 2 : 5. Both classes had the same number of girls. When 32 boys from Primary 4 Peace joined Primary 4 Goodness, the ratio of the number of girls to the number of boys in Primary 4 Peace became 1 : 2. Find the total enrolment of both classes.
Primary 4 Peace |
Primary 4 Goodness |
Girls |
Boys |
Girls |
Boys |
1x2 |
4x2 |
2x1 |
5x1 |
1x2 |
|
1x2 |
|
2 u |
8 u |
2 u |
5 u |
The number of girls in both classes is the same. Make the number of girls the same. LCM of 1 and 2 is 2.
|
Primary 4 Peace |
Primary 4 Goodness |
|
Girls |
Boys |
Girls |
Boys |
Before |
2 u |
8 u |
2 u |
5 u |
Change |
|
- 32 |
|
+ 32 |
After |
1x2 = 2 u |
2x2 = 4 u |
2 u |
5 u + 32 |
The number of girls in Primary 4 Peace remains unchanged. Make the number of girls in Primary 4 the same. LCM of 2 and 1 is 2.
Number of boys from Primary 4 Peace that joined Primary 4 Goodness
= 8 u - 4 u
= 4 u
4 u = 32
1 u = 32 ÷ 4 = 8
Total enrolment of both classes
= 2 u + 8 u + 2 u + 5 u
= 17 u
= 17 x 8
= 136
Answer(s): 136