Three types of bread flour, B, C and D come in containers of 90 g, 120 g and 180 g respectively. Containers of B, C and D are mixed together in the ratio 1 : 2 : 3 to obtain 8.7 kg of an assortment of bread flour.

1. How many containers of B and C are used altogether?
2. Find the difference between the combined weight of all the bread flour in containers C and containers D as compared to the bread flour in containers B. Express the weight in kilograms.

	B	C	D
Number	1 u	2 u	3 u
Value	90	120	180
Total value	90 u	240 u	540 u

(a)
Total mass of bread flour
= 90 u + 240 u + 540 u
= 870 u

870 u = 8700

1 u = 8700 ÷ 870 = 10

Total number of containers of B and C used
= 1 u + 2 u
= 3 u
= 3 x 10
= 30 

(b)
Combined weight of all the bread flour in containers C and containers D
= 240 u + 540 u
= 780 u

Difference between the combined weight of all the bread flour in containers C and containers D as compared to the bread flour in containers B
= 780 u - 90 u
= 690 u
= 690 x 10
= 6900 g
= 6.9 kg 

Answer(s): (a) 30; (b) 6.9 kg