Hello!
1.
To find the area of a rectangular prism you use the equation
2(wl + wh + lh)
w is width
l is length
h is height
Put in the values
2(5 * 12 + 5 * 9 + 12 * 9)
Combine like terms
2(60 + 45 + 108)
Add
2(213)
Multiply
The area is 426
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2.
The area of a cylinder uses the equation
Put in the values you know and 3.14 for pi
Solve this and you get 411.968
Round
The answer is 412 cm squared
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3.
A cereal box is a rectangular prism
You use the equation from 1 and it does not matter what values you use for what side
2(wl + wh + lh)
2(11 * 8 + 11 * 6 + 8 * 6)
2(202)
multiply
The answer is 404in squared
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4.
The equation for the volume is whl
w is width
h is height
l is length
Put in the values
4 * 2 * 1
The answer is 8
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5.
The equation for volume is V = whl
Put in the values you know
120 = 8 * 5 * h
Divide both sides by 8
15 = 5 * h
Divide both sides by 5
3 = h
The answer is 3cm
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Hope this helps!