The number of boys to the number of girls in Primary 2 Gentleness was 1 : 4. The number of boys to the number of girls in Primary 2 Faithfulness was 4 : 5. Both classes had the same number of boys. When 16 girls from Primary 2 Gentleness joined Primary 2 Faithfulness, the ratio of the number of boys to the number of girls in Primary 2 Gentleness became 1 : 2. Find the total enrolment of both classes.
Primary 2 Gentleness |
Primary 2 Faithfulness |
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 2 Gentleness |
Primary 2 Faithfulness |
|
Boys |
Girls |
Boys |
Girls |
Before |
4 u |
16 u |
4 u |
5 u |
Change |
|
- 16 |
|
+ 16 |
After |
1x4 = 4 u |
2x4 = 8 u |
4 u |
5 u + 16 |
The number of boys in Primary 2 Gentleness remains unchanged. Make the number of boys in Primary 2 the same. LCM of 4 and 1 is 4.
Number of girls from Primary 2 Gentleness that joined Primary 2 Faithfulness
= 16 u - 8 u
= 8 u
8 u = 16
1 u = 16 ÷ 8 = 2
Total enrolment of both classes
= 4 u + 16 u + 4 u + 5 u
= 29 u
= 29 x 2
= 58
Answer(s): 58