Three types of rice flour, P, Q and R come in containers of 120 g, 150 g and 180 g respectively. Containers of P, Q and R are mixed together in the ratio 2 : 3 : 4 to obtain 16.92 kg of an assortment of rice flour.

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

	P	Q	R
Number	2 u	3 u	4 u
Value	120	150	180
Total value	240 u	450 u	720 u

(a)
Total mass of rice flour
= 240 u + 450 u + 720 u
= 1410 u

1410 u = 16920

1 u = 16920 ÷ 1410 = 12

Total number of containers of P and Q used
= 2 u + 3 u
= 5 u
= 5 x 12
= 60 

(b)
Combined weight of all the rice flour in containers Q and containers R
= 450 u + 720 u
= 1170 u

Difference between the combined weight of all the rice flour in containers Q and containers R as compared to the rice flour in containers P
= 1170 u - 240 u
= 930 u
= 930 x 12
= 11160 g
= 11.16 kg 

Answer(s): (a) 60; (b) 11.16 kg