Question

John buys 3 packets of washing powder A. and 5 packets of washing

powder B. and spends #4 900. john has 3 packets of washing powder
B that is not needed and returns these to the shop and gets a full
refund. He also buys 6 further packets of washing powder john pays an #1740 in addition to the money received as refund.
How much does a packer of each washing powder cost:
A costs 600.
B costs 620​

Answer 1

A costs #711.5385

B costs #553.0769

Explanation:

Let cost of powder A be x and powder B be y

When he’s given refund, equation can be written as

6x=1740+3y

6x-3y=1740 eqn 1

2x-y=870 making y the subject of the formula

Y=2x-870

Also, from the initial shopping

3x+5y=4900 eqn 2

Substituting the formula of y into eqn 2 we obtain

3x+5(2x-870)=4900

3x+10x-4350=4900

13x=4900+4350=9250

X=9250/13= 711.5385

Y=2x-870=2(711.5385)-870= 553.0769