The number of boys to the number of girls in Primary 1 Patience was 3 : 5. The number of boys to the number of girls in Primary 1 Love was 5 : 6. Both classes had the same number of boys. When 14 girls from Primary 1 Patience joined Primary 1 Love, the ratio of the number of boys to the number of girls in Primary 1 Patience became 5 : 6. Find the total enrolment of both classes.

Primary 1 Patience		Primary 1 Love
Boys	Girls	Boys	Girls
3x5	5x5	5x3	6x3
1x15		1x15
15 u	25 u	15 u	18 u

The number of boys in both classes is the same.  Make the number of boys the same.  LCM of 3 and 5 is 15.

	Primary 1 Patience		Primary 1 Love
	Boys	Girls	Boys	Girls
Before	15 u	25 u	15 u	18 u
Change		- 14		+ 14
After	5x3 = 15 u	6x3 = 18 u	15 u	18 u + 14

The number of boys in Primary 1 Patience remains unchanged.  Make the number of boys in Primary 1 the same.  LCM of 15 and 5 is 15.

Number of girls from Primary 1 Patience that joined Primary 1 Love
= 25 u - 18 u
= 7 u

7 u = 14

1 u = 14 ÷ 7 = 2

Total enrolment of both classes
= 15 u + 25 u + 15 u + 18 u
= 73 u
= 73 x 2
= 146

Answer(s): 146