Problema Solution
An open-top box containing 480 cm is made by cutting out a 5cm by 5cm square from each corner of a square piece of metal and turning up the side. Find the dimensions of the original piece of metal
Answer provided by our tutors
Volume = 480cm
Let the length of any side of the original sqare piece of metal = x.
Length = x-5
Width = x-5
Height = 5
You really have to picture this, try drawing it out. When you cut out 5*5 squares, and fold up the sides, the height wil equal 5. The length and width are x-5 because you are subtracting 5 from each side of a square.
Volume = l*w*h
Substitute in the above values and solve for x
480=(x-5)*(x-5)*5
96=(x-5)(x-5)
96=x^2 - 10x + 25
0 = x^2 - 10x - 71
Use the quadratic formula to solve for x.
x = -b +/- (sqrt(b^2-4ac))/2a
a:1 b:-10 c:-71
x = (10 +/- sqrt(100-(-284)))/2
x = (10 +/- sqrt(100+284))/2
x = (10 +/- sqrt(384)/2
x = (10+19.6)/2 or x= (10-19.6)/2
Choose the first because the dimensions have to be positive:
x = 14.8. The dimensions are approximately 14.8 cm by 14.8 cm
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