The number of boys to the number of girls in Primary 4 Faithfulness was 2 : 5. The number of boys to the number of girls in Primary 4 Love was 3 : 5. Both classes had the same number of boys. When 35 girls from Primary 4 Faithfulness joined Primary 4 Love, the ratio of the number of boys to the number of girls in Primary 4 Faithfulness became 3 : 4. Find the total enrolment of both classes.

Primary 4 Faithfulness		Primary 4 Love
Boys	Girls	Boys	Girls
2x3	5x3	3x2	5x2
1x6		1x6
6 u	15 u	6 u	10 u

The number of boys in both classes is the same.  Make the number of boys the same.  LCM of 2 and 3 is 6.

	Primary 4 Faithfulness		Primary 4 Love
	Boys	Girls	Boys	Girls
Before	6 u	15 u	6 u	10 u
Change		- 35		+ 35
After	3x2 = 6 u	4x2 = 8 u	6 u	10 u + 35

The number of boys in Primary 4 Faithfulness remains unchanged.  Make the number of boys in Primary 4 the same.  LCM of 6 and 3 is 6.

Number of girls from Primary 4 Faithfulness that joined Primary 4 Love
= 15 u - 8 u
= 7 u

7 u = 35

1 u = 35 ÷ 7 = 5

Total enrolment of both classes
= 6 u + 15 u + 6 u + 10 u
= 37 u
= 37 x 5
= 185

Answer(s): 185