Answer:
11.3
Step-by-step explanation:
First solve how many grams of each mineral you need.
To do this use this equation
[tex]\frac{3}{5} =\frac{x}{y} ; x+y=400[/tex]
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
[tex]x=\frac{150}{1000}; y=\frac{250}{1000}[/tex]
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
