Question 104282: You are going to make a box out of cardboard. The box needs to measure 10 cm by 5 cm by 5 cm; 10% of the final product will be wasted in the cutting process. How much cardboard do you need?
Answer by mathnard(10)   (Show Source):
You can put this solution on YOUR website! The answer should be 275 square centimeters. Here's why:
This is a surface area problem.
First, let me calculate the surface area of this box. Let's assume that it is 10 cm tall, but that if you set it on a table, its base is 5 cm by 5 cm.
Wouldn't you agree that the bottom and top will each have an area of 25 sq. cm.?
And each of the 4 sides will have an area of 10x5 or 50 sq. cm.?
Bases + Sides = total surface area
2(25)+4(50)=250 sq cm
Now we encounter trouble. Apparently, some of the material was wasted while we made the box. In fact, 10% of our final product. Because of the way this problem was written, I am going to assume that we mean 10% of the 250 square centimeters was how much cardboard was wasted. This would mean that 0.10(250) or 25 square centimeters of cardboard was wasted.
Altogether, we would have 250+25 (or 275) square centimeters of cardboard needed.
This should be the correct answer, but IF your teacher MEANT to say that in the process, 10% of the ORIGINAL amount of cardboard was wasted, we would need to set up an equation like this:
0.90(x)=250
In other words, if 10% was wasted, then 90% is still there.
90% of the original amount (x) is equal to 250.
If this is what your teacher meant, then the answer would be 250/0.90 or
277.8 square centimeters.
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