The number of girls to the number of boys in Primary 3 Patience was 2 : 5. The number of girls to the number of boys in Primary 3 Kindness was 4 : 5. Both classes had the same number of girls. When 12 boys from Primary 3 Patience joined Primary 3 Kindness, the ratio of the number of girls to the number of boys in Primary 3 Patience became 2 : 3. Find the total enrolment of both classes.
Primary 3 Patience |
Primary 3 Kindness |
Girls |
Boys |
Girls |
Boys |
2x2 |
5x2 |
4x1 |
5x1 |
1x4 |
|
1x4 |
|
4 u |
10 u |
4 u |
5 u |
The number of girls in both classes is the same. Make the number of girls the same. LCM of 2 and 4 is 4.
|
Primary 3 Patience |
Primary 3 Kindness |
|
Girls |
Boys |
Girls |
Boys |
Before |
4 u |
10 u |
4 u |
5 u |
Change |
|
- 12 |
|
+ 12 |
After |
2x2 = 4 u |
3x2 = 6 u |
4 u |
5 u + 12 |
The number of girls in Primary 3 Patience remains unchanged. Make the number of girls in Primary 3 the same. LCM of 4 and 2 is 4.
Number of boys from Primary 3 Patience that joined Primary 3 Kindness
= 10 u - 6 u
= 4 u
4 u = 12
1 u = 12 ÷ 4 = 3
Total enrolment of both classes
= 4 u + 10 u + 4 u + 5 u
= 23 u
= 23 x 3
= 69
Answer(s): 69