The number of boys to the number of girls in Primary 1 Gentleness was 1 : 4. The number of boys to the number of girls in Primary 1 Patience was 4 : 5. Both classes had the same number of boys. When 40 girls from Primary 1 Gentleness joined Primary 1 Patience, the ratio of the number of boys to the number of girls in Primary 1 Gentleness became 1 : 2. Find the total enrolment of both classes.
Primary 1 Gentleness |
Primary 1 Patience |
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 1 Gentleness |
Primary 1 Patience |
|
Boys |
Girls |
Boys |
Girls |
Before |
4 u |
16 u |
4 u |
5 u |
Change |
|
- 40 |
|
+ 40 |
After |
1x4 = 4 u |
2x4 = 8 u |
4 u |
5 u + 40 |
The number of boys in Primary 1 Gentleness remains unchanged. Make the number of boys in Primary 1 the same. LCM of 4 and 1 is 4.
Number of girls from Primary 1 Gentleness that joined Primary 1 Patience
= 16 u - 8 u
= 8 u
8 u = 40
1 u = 40 ÷ 8 = 5
Total enrolment of both classes
= 4 u + 16 u + 4 u + 5 u
= 29 u
= 29 x 5
= 145
Answer(s): 145