The number of girls to the number of boys in Primary 2 Kindness was 2 : 5. The number of girls to the number of boys in Primary 2 Love was 5 : 6. Both classes had the same number of girls. When 30 boys from Primary 2 Kindness joined Primary 2 Love, the ratio of the number of girls to the number of boys in Primary 2 Kindness became 2 : 3. Find the total enrolment of both classes.

Primary 2 Kindness		Primary 2 Love
Girls	Boys	Girls	Boys
2x5	5x5	5x2	6x2
1x10		1x10
10 u	25 u	10 u	12 u

The number of girls in both classes is the same.  Make the number of girls the same.  LCM of 2 and 5 is 10.

	Primary 2 Kindness		Primary 2 Love
	Girls	Boys	Girls	Boys
Before	10 u	25 u	10 u	12 u
Change		- 30		+ 30
After	2x5 = 10 u	3x5 = 15 u	10 u	12 u + 30

The number of girls in Primary 2 Kindness remains unchanged.  Make the number of girls in Primary 2 the same.  LCM of 10 and 2 is 10.

Number of boys from Primary 2 Kindness that joined Primary 2 Love
= 25 u - 15 u
= 10 u

10 u = 30

1 u = 30 ÷ 10 = 3

Total enrolment of both classes
= 10 u + 25 u + 10 u + 12 u
= 57 u
= 57 x 3
= 171

Answer(s): 171