The number of boys to the number of girls in Primary 4 Love was 1 : 4. The number of boys to the number of girls in Primary 4 Gentleness was 4 : 5. Both classes had the same number of boys. When 12 girls from Primary 4 Love joined Primary 4 Gentleness, the ratio of the number of boys to the number of girls in Primary 4 Love became 1 : 3. Find the total enrolment of both classes.
Primary 4 Love |
Primary 4 Gentleness |
Boys |
Girls |
Boys |
Girls |
1x4 |
4x4 |
4x1 |
5x1 |
1x4 |
|
1x4 |
|
4 u |
16 u |
4 u |
5 u |
The number of boys in both classes is the same. Make the number of boys the same. LCM of 1 and 4 is 4.
|
Primary 4 Love |
Primary 4 Gentleness |
|
Boys |
Girls |
Boys |
Girls |
Before |
4 u |
16 u |
4 u |
5 u |
Change |
|
- 12 |
|
+ 12 |
After |
1x4 = 4 u |
3x4 = 12 u |
4 u |
5 u + 12 |
The number of boys in Primary 4 Love remains unchanged. Make the number of boys in Primary 4 the same. LCM of 4 and 1 is 4.
Number of girls from Primary 4 Love that joined Primary 4 Gentleness
= 16 u - 12 u
= 4 u
4 u = 12
1 u = 12 ÷ 4 = 3
Total enrolment of both classes
= 4 u + 16 u + 4 u + 5 u
= 29 u
= 29 x 3
= 87
Answer(s): 87