The number of boys to the number of girls in Primary 2 Goodness was 2 : 5. The number of boys to the number of girls in Primary 2 Kindness was 4 : 5. Both classes had the same number of boys. When 14 girls from Primary 2 Goodness joined Primary 2 Kindness, the ratio of the number of boys to the number of girls in Primary 2 Goodness became 1 : 2. Find the total enrolment of both classes.
Primary 2 Goodness |
Primary 2 Kindness |
Boys |
Girls |
Boys |
Girls |
2x2 |
5x2 |
4x1 |
5x1 |
1x4 |
|
1x4 |
|
4 u |
10 u |
4 u |
5 u |
The number of boys in both classes is the same. Make the number of boys the same. LCM of 2 and 4 is 4.
|
Primary 2 Goodness |
Primary 2 Kindness |
|
Boys |
Girls |
Boys |
Girls |
Before |
4 u |
10 u |
4 u |
5 u |
Change |
|
- 14 |
|
+ 14 |
After |
1x4 = 4 u |
2x4 = 8 u |
4 u |
5 u + 14 |
The number of boys in Primary 2 Goodness 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 Goodness that joined Primary 2 Kindness
= 10 u - 8 u
= 2 u
2 u = 14
1 u = 14 ÷ 2 = 7
Total enrolment of both classes
= 4 u + 10 u + 4 u + 5 u
= 23 u
= 23 x 7
= 161
Answer(s): 161