Question

A trader mixes Coffee A which costs $9 per kg with Coffee B which costs $13 per kg and Coffee C which costs $15 per kg, in the ratio 4:3:1. The mixture is then sold at $1.80 per 100 g. Express his profit or loss as a percentage of his cost price.

Answer 1

Coffee A : B : C = 4:3:1
= 4x : 3x : x , where these parts are expressed in kg
so he bought 8x kg of coffee


Cost of mixture = 9(4x) + 13(3x) + 15x = $90x

selling price = $1.80/100 g = $18 / kg

and he has 8x kg to sell
so return from sale = $18(8x)

profit = $(18(8x) - 90x) = $54x

percentage of profit = 54x / 90x = .6 = 60%


check:
suppose he bought 4kg, 3kg, and 1kg of the corresponding mixture
he bought this for 9(4) + 13(3) + 15 or a total of $90
so he has 8 kg so sell at 1.80/100 g or at $18/kg
return after sale = 18(8) = $144
profit = 144-90 = $54

percentage profit = 54/90 = .6 or 60%