SOLUTION: Question An open water tank with length 20 cm and width 15 cm holds 4.8 litres of water. Calculate the height of the water level in the tank and the total surface area of the c

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Question 42075: Question
An open water tank with length 20 cm and width 15 cm holds 4.8 litres of water. Calculate the height of the water level in the tank and the total surface area of the cuboid in contact with the water.
This is what I have done
4.8 litre = 4800 cm^3 (cm cube) since 1 litre = 100cm^3
Let the height of the water level = h
Volume
= Length x width x height = 4800
20 x 15 x h = 4800
300h = 4800
h = 4800/300
h=16
Total surface area of the cuboid
= 2 ((length x width) + (length x height) + (width x height))
= 2 ((20 x 15) + (20 x 16) + (15 x 16))
= 2 (300 + 320 + 240)
= 2 (1100)
= 2200
But my teacher said that the answer is 1420 (for the total surface area). Who is right in this case ?
Please help. Tahnk you very much.
Found 2 solutions by kev82, raiumarshair:
Answer by kev82(151) (Show Source):
You can put this solution on YOUR website!
Firstly, there is a slight problem in your maths
300+320+240=860, not 1100. So by your reckoning the surface area should be 2*860=1720. However, the tank is open, meaning it doesn't have a top. What do you get if you take off the surface area of the top from 1720?
Hope that helps,
Kev

Answer by raiumarshair(1) (Show Source):
You can put this solution on YOUR website!
Your teacher is right. When we add all surface areas then it is called total surface area. In your question tank is open from top so it has only 5 surface areas not 6 Because top surface area is not available. So we add like this
Total surface area= 1(length�width)+2 (length�hight)+2 (width�hight)
Your answer willbe like your techer 1420