Question

High grade steel consists of 85% iron and 15% magnese. Low grade steel consists of 67% iron and 33% mag ese. NASA orders 500 tons of steel and specifies that it must be in the proportion 80% iron and 20% steel. How many tons of high grade and low grade steel must you melt together to create steel that matches NASA’s requirements?

Answer 1

Answer:

$361\dfrac{1}{9}$ tons of high steel and $138\dfrac{8}{9}$ tons of low steel

Step-by-step explanation:

Let x be the number of tons of high grade steel and y be the number of tons ow low grade steel needed.

In x tons of high grade steel there are

$0.85x$ tons of iron

$0.15x$ tons of magnese

In y tons of low grade steel there are

$0.67y$ tons of iron

$0.33y$ tons of magnese

NASA orders 500 tons of steel, so

$x+y=500$

and specifies that it must be in the proportion 80% iron and 20% magnese, so

$0.85x+0.67y=500\cdot 0.8\\ \\0.85x+0.67y=400$

From the first equation,

$x=500-y$

Substitute it into the second equation:

$0.85(500-y)+0.67y=400\\ \\425-0.85y+0.67y=400\\ \\-0.18y=-25\\ \\y=\dfrac{2,500}{18}=138\dfrac{8}{9}\ tons\\ \\x=361\dfrac{1}{9}\ tons$