The number of boys to the number of girls in Primary 6 Goodness was 2 : 5. The number of boys to the number of girls in Primary 6 Faithfulness was 3 : 4. Both classes had the same number of boys. When 24 girls from Primary 6 Goodness joined Primary 6 Faithfulness, the ratio of the number of boys to the number of girls in Primary 6 Goodness became 2 : 3. Find the total enrolment of both classes.
| Primary 6 Goodness |
Primary 6 Faithfulness |
| Boys |
Girls |
Boys |
Girls |
| 2x3 |
5x3 |
3x2 |
4x2 |
| 1x6 |
|
1x6 |
|
| 6 u |
15 u |
6 u |
8 u |
The number of boys in both classes is the same. Make the number of boys the same. LCM of 2 and 3 is 6.
| |
Primary 6 Goodness |
Primary 6 Faithfulness |
| |
Boys |
Girls |
Boys |
Girls |
| Before |
6 u |
15 u |
6 u |
8 u |
| Change |
|
- 24 |
|
+ 24 |
| After |
2x3 =
6 u |
3x3 =
9 u |
6 u |
8 u + 24 |
The number of boys in Primary 6 Goodness remains unchanged. Make the number of boys in Primary 6 the same. LCM of 6 and 2 is 6.
Number of girls from Primary 6 Goodness that joined Primary 6 Faithfulness
= 15 u - 9 u
= 6 u
6 u = 24
1 u = 24 ÷ 6 = 4
Total enrolment of both classes
= 6 u + 15 u + 6 u + 8 u
= 35 u
= 35 x 4
= 140
Answer(s): 140
