Wednesday, April 19, 2006

darie's volume and surface area questions

Problem 1. (easy)
1. How much cement is needed to build a sidewalk that is one thousand, one hundred twenty metres long, four metres wide and fifty centimetres thick? Round your answer to the nearest cubic metre.

just need to multiply all the numbers together. *since it's cm and not meters, you need to divided 50 by 100. and that'll give you 0.5 .
1120 x 4 x 0.5 = 2240 m2

so you need 2240 m2 t build the sidewalk.


Problem 2 (harder)
2. Mr. Bloop has a cylindrical water tank on his farm. It is three metres long and 60 centimetres in diameter. Water flows out a valve in the bottom of the tank at a rate of 0.8 cubic metres per second. How long will it take the tank to empty?

...i don't get it...


Problem 3 (easy)
3. If you have five 5 cm by 5 cm x 5 cm aluminum cubes and superglue them together in a row, what is the surface area of the resulting shape made by the five cubes?

5 x 5 = 25 } one side of one cube
25 x 5 = 125 cm 2 } six sides of one cube
125 x 5 = 625 cm 2 } all the sides.
since all the sides are going to be put together you have to take away 4 sides.

so it'll be

4 x 25 = 100
625 - 100 = 525 cm2

surface area is 525 cm2

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