Determine the amount you need to invest to have $22,000 dollars in 4 years if you invest at 5% annual interest, compounded quart
1 answer:
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Answer:
tons of high steel and
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
tons of iron
tons of magnese
In y tons of low grade steel there are
tons of iron
tons of magnese
NASA orders 500 tons of steel, so
and specifies that it must be in the proportion 80% iron and 20% magnese, so
From the first equation,
Substitute it into the second equation:
Let be the unknown number. So, three times that number means
, and the square of the number is
We have to sum 528 and three times the number, so we have
Then, we have to subtract this number from , so we have
The result is 120, so the equation is
This is a quadratic equation, i.e. an equation like . These equation can be solved - assuming they have a solution - with the following formula
If you plug the values from your equation, you have
So, the two solutions would be
But we know that x is positive, so we only accept the solution