The number of boys to the number of girls in Primary 6 Kindness was 1 : 4. The number of boys to the number of girls in Primary 6 Goodness was 2 : 5. Both classes had the same number of boys. When 12 girls from Primary 6 Kindness joined Primary 6 Goodness, the ratio of the number of boys to the number of girls in Primary 6 Kindness became 1 : 3. Find the total enrolment of both classes.
Primary 6 Kindness |
Primary 6 Goodness |
Boys |
Girls |
Boys |
Girls |
1x2 |
4x2 |
2x1 |
5x1 |
1x2 |
|
1x2 |
|
2 u |
8 u |
2 u |
5 u |
The number of boys in both classes is the same. Make the number of boys the same. LCM of 1 and 2 is 2.
|
Primary 6 Kindness |
Primary 6 Goodness |
|
Boys |
Girls |
Boys |
Girls |
Before |
2 u |
8 u |
2 u |
5 u |
Change |
|
- 12 |
|
+ 12 |
After |
1x2 = 2 u |
3x2 = 6 u |
2 u |
5 u + 12 |
The number of boys in Primary 6 Kindness remains unchanged. Make the number of boys in Primary 6 the same. LCM of 2 and 1 is 2.
Number of girls from Primary 6 Kindness that joined Primary 6 Goodness
= 8 u - 6 u
= 2 u
2 u = 12
1 u = 12 ÷ 2 = 6
Total enrolment of both classes
= 2 u + 8 u + 2 u + 5 u
= 17 u
= 17 x 6
= 102
Answer(s): 102