An alloy is made by mixing metals A and B in the ratio 3:5 metal a costs £42 per kg
metal b costs £20 per kg

how much would it cost to make 400g of the alloy?

11.3

Step-by-step explanation:

First solve how many grams of each mineral you need.

To do this use this equation

Solve the system of equations to get

x=150, y=250

Since there are 1000 grams in 1 kg then the amount of kg of each material you need will be

So you need to 0.15 of a kg of mineral a and 0.25 kg of mineral b.

Multiply 0.15 by 42 to get the amount of money needed to buy mineral a.

0.15*42=6.3

Multiply 0.25 by 20 get the amount of money needed to buy mineral b.

0.25*20= 5

Add them to get the final amount

6.3+5=11.3

you can use a^2+ b^2=c^2