Question

A knife is three times the cost of a spoon.

9 spoons and 12 knives cost £82.80
Work out the cost of 1 knife

Answer 1

Answer: 1 knife costes £5.52

Explanation:

Let a knife costes £x and a spoon costes £y

Hence, we obtain a system of equations:

x=3y (1)

12x+9y=82.80 (2)

Divide both parts of the equation (2) by 3:

x=3y

4x+3y=27.6 (3)

We substitute the value of x=3u into equation (3):

4(3y)+3y=27.6

12y+3y=27.6

15y=27.6

Divide both parts of the equation by 15:

y=£1.84

x=3y

x=3(1.84)

x=£5.52