In what ratio should a variety of Rice costing Rs. 20 per kg be mixed with another variety of Rice costing Rs. 31.50 per kg to obtain a mixture costing Rs. 23.75 per kg?
Choose the correct choice from the following answers:
A) 16 : 30
B) 30 : 14
C) 16 : 31
D) 31 : 15
E) 15 : 31
Let us say the ratio of the quantities of cheaper and dearer varieties = x : y   By the rule of allegation, x/y = (31.50 - 23.75) / (23.75 - 20) = 31/15   ANSWER:31 : 15
<result>D</result>
In what ratio should a variety of Rice costing Rs. 20 per kg be mixed with another variety of Rice costing Rs. 31.50 per kg to obtain a mixture costing Rs. 23.75 per kg?