Three types of bread flour, N, P and Q come in containers of 120 g, 180 g and 240 g respectively. Containers of N, P and Q are mixed together in the ratio 3 : 4 : 7 to obtain 33.12 kg of an assortment of bread flour.

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

	N	P	Q
Number	3 u	4 u	7 u
Value	120	180	240
Total value	360 u	720 u	1680 u

(a)
Total mass of bread flour
= 360 u + 720 u + 1680 u
= 2760 u

2760 u = 33120

1 u = 33120 ÷ 2760 = 12

Total number of containers of N and P used
= 3 u + 4 u
= 7 u
= 7 x 12
= 84 

(b)
Combined weight of all the bread flour in containers P and containers Q
= 720 u + 1680 u
= 2400 u

Difference between the combined weight of all the bread flour in containers P and containers Q as compared to the bread flour in containers N
= 2400 u - 360 u
= 2040 u
= 2040 x 12
= 24480 g
= 24.48 kg 

Answer(s): (a) 84; (b) 24.48 kg