The number of girls to the number of boys in Primary 3 Gentleness was 1 : 4. The number of girls to the number of boys in Primary 3 Love was 5 : 6. Both classes had the same number of girls. When 25 boys from Primary 3 Gentleness joined Primary 3 Love, the ratio of the number of girls to the number of boys in Primary 3 Gentleness became 1 : 3. Find the total enrolment of both classes.
Primary 3 Gentleness |
Primary 3 Love |
Girls |
Boys |
Girls |
Boys |
1x5 |
4x5 |
5x1 |
6x1 |
1x5 |
|
1x5 |
|
5 u |
20 u |
5 u |
6 u |
The number of girls in both classes is the same. Make the number of girls the same. LCM of 1 and 5 is 5.
|
Primary 3 Gentleness |
Primary 3 Love |
|
Girls |
Boys |
Girls |
Boys |
Before |
5 u |
20 u |
5 u |
6 u |
Change |
|
- 25 |
|
+ 25 |
After |
1x5 = 5 u |
3x5 = 15 u |
5 u |
6 u + 25 |
The number of girls in Primary 3 Gentleness remains unchanged. Make the number of girls in Primary 3 the same. LCM of 5 and 1 is 5.
Number of boys from Primary 3 Gentleness that joined Primary 3 Love
= 20 u - 15 u
= 5 u
5 u = 25
1 u = 25 ÷ 5 = 5
Total enrolment of both classes
= 5 u + 20 u + 5 u + 6 u
= 36 u
= 36 x 5
= 180
Answer(s): 180