Erika and Risa used the same number of chocolate chips to bake cakes. Erika used ³₇ of her chocolate chips and Risa used ⁴₇ of her chocolate chips. They had a total of 490 chocolate chips at first.

1. How many chocolate chips did each girl use?
2. How many chocolate chips did both girls have left altogether?

	Erika	Risa	Total
Before	7x4 = 28 u	7x3 = 21 u	49 u
Change	- 3x4 = - 12 u	- 4x3 = - 12 u
After	4x4 = 16 u	3x3 = 9 u	25 u

(a)
Erika and Risa used the same number of chocolate chips to bake cakes.  Make the numerators the same. LCM of 3 and 4 is 12. 
3x47x4 of Mary's chocolate chips = 4x37x3 of Risa's chocolate chips 
1228 of Mary's chocolate chips = 1221 of Risa's chocolate chips 

Total number of chocolate chips at first
= 28 u + 21 u
= 49 u

49 u = 490

1 u = 490 ÷ 49 = 10

Number of chocolate chips that each girl used
= 12 u
= 12 x 10
= 120 

(b)
Total number of chocolate chips that both girls had left 
= 16 u + 9 u
= 25 u
= 25 x 10
= 250

Answer(s): (a) 120; (b) 250