Three types of sugar, Q, R and S come in containers of 80 g, 120 g and 200 g respectively. Containers of Q, R and S are mixed together in the ratio 2 : 5 : 7 to obtain 15.12 kg of an assortment of sugar.

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

	Q	R	S
Number	2 u	5 u	7 u
Value	80	120	200
Total value	160 u	600 u	1400 u

(a)
Total mass of sugar
= 160 u + 600 u + 1400 u
= 2160 u

2160 u = 15120

1 u = 15120 ÷ 2160 = 7

Total number of containers of Q and R used
= 2 u + 5 u
= 7 u
= 7 x 7
= 49 

(b)
Combined weight of all the sugar in containers R and containers S
= 600 u + 1400 u
= 2000 u

Difference between the combined weight of all the sugar in containers R and containers S as compared to the sugar in containers Q
= 2000 u - 160 u
= 1840 u
= 1840 x 7
= 12880 g
= 12.88 kg 

Answer(s): (a) 49; (b) 12.88 kg