Question

In what ratio must a grocer mix two varieties of tea costing Rs. 15 and Rs.
20 per kg respectively

so as to get a mixture worth Rs. 16.50 per kg
? 

Answer 1

let us say that the grocer mixes x kg of the tea worth Rs.15/kg and y kg of tea worth Rs.20/kg. therefore he would get (x+y) kg tea worth Rs.16.5 kg.
hence$15x+20y=16.5(x+y)$⇒$(20-16.5)y=(16.5-15)x$⇒$3.5y=1.5x$⇒$y/x=1.5/3.5=15/35=3/7$⇒$x/y=7/3$.
hence ratio=7/3