n what ratio should a variety of rice costing Rs. 6 per kg be mixed with another variety of rice costing Rs. 8.75 per kg to obtain a mixture costing Rs. 7.50 per kg?

A. 5 : 6
B. 3 : 4
C. 7 : 8
D. 8 : 9

Explanation:
Let us say the ratio of the quantities of cheaper and dearer varieties = x : y
By the rule of allegation, x/y = (87.5 – 7.50) / (7.50 – 6) = 5/6