Question

How many kilogram of sugar costing Rs. 9 per kg must be mixed with 27 kg of sugar costing Rs. 7 per kg so that there may be a gain of 10% by selling the mixture at Rs. 9.24 per kg?

Answer 1

S.P. of 1 kg of mixture=Rs 9.24,gain 10%
C.P. of 1 kg of mixture=100/110 ×9.24= Rs. 8.40 
by the rule of allilation we have:
C.P. of 1 kg sugar of 1 st kind
cost of 1 kg of sugar of 2 nd kind 
Rs.9              mean price                Rs.7
1.40                  Rs. 8.40                  0.60
ratio of quantities of 1 st and 2 nd kind = 14:6=7:3
let x kg of sugar of 1 st be mixed with 27 kg of 2 nd kind.
then,7:3=x:27
x=7×27/3 = 63kg..