The number of girls to the number of boys in Primary 6 Faithfulness was 1 : 4. The number of girls to the number of boys in Primary 6 Gentleness was 4 : 5. Both classes had the same number of girls. When 24 boys from Primary 6 Faithfulness joined Primary 6 Gentleness, the ratio of the number of girls to the number of boys in Primary 6 Faithfulness became 2 : 5. Find the total enrolment of both classes.
Primary 6 Faithfulness |
Primary 6 Gentleness |
Girls |
Boys |
Girls |
Boys |
1x4 |
4x4 |
4x1 |
5x1 |
1x4 |
|
1x4 |
|
4 u |
16 u |
4 u |
5 u |
The number of girls in both classes is the same. Make the number of girls the same. LCM of 1 and 4 is 4.
|
Primary 6 Faithfulness |
Primary 6 Gentleness |
|
Girls |
Boys |
Girls |
Boys |
Before |
4 u |
16 u |
4 u |
5 u |
Change |
|
- 24 |
|
+ 24 |
After |
2x2 = 4 u |
5x2 = 10 u |
4 u |
5 u + 24 |
The number of girls in Primary 6 Faithfulness remains unchanged. Make the number of girls in Primary 6 the same. LCM of 4 and 2 is 4.
Number of boys from Primary 6 Faithfulness that joined Primary 6 Gentleness
= 16 u - 10 u
= 6 u
6 u = 24
1 u = 24 ÷ 6 = 4
Total enrolment of both classes
= 4 u + 16 u + 4 u + 5 u
= 29 u
= 29 x 4
= 116
Answer(s): 116