The number of girls to the number of boys in Primary 5 Goodness was 2 : 5. The number of girls to the number of boys in Primary 5 Joy was 3 : 5. Both classes had the same number of girls. When 24 boys from Primary 5 Goodness joined Primary 5 Joy, the ratio of the number of girls to the number of boys in Primary 5 Goodness became 2 : 3. Find the total enrolment of both classes.
| Primary 5 Goodness |
Primary 5 Joy |
| Girls |
Boys |
Girls |
Boys |
| 2x3 |
5x3 |
3x2 |
5x2 |
| 1x6 |
|
1x6 |
|
| 6 u |
15 u |
6 u |
10 u |
The number of girls in both classes is the same. Make the number of girls the same. LCM of 2 and 3 is 6.
| |
Primary 5 Goodness |
Primary 5 Joy |
| |
Girls |
Boys |
Girls |
Boys |
| Before |
6 u |
15 u |
6 u |
10 u |
| Change |
|
- 24 |
|
+ 24 |
| After |
2x3 =
6 u |
3x3 =
9 u |
6 u |
10 u + 24 |
The number of girls in Primary 5 Goodness remains unchanged. Make the number of girls in Primary 5 the same. LCM of 6 and 2 is 6.
Number of boys from Primary 5 Goodness that joined Primary 5 Joy
= 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 + 10 u
= 37 u
= 37 x 4
= 148
Answer(s): 148
