Find the length of the tank

Find the length of the tank

Postby Chikis » Wed Feb 19, 2014 8:22 pm

An open rectangular tank is made from a steel plate of area 1440 m^2. Its lenght is twice it width. If the depth of the tank is 4m less than the width, find the length of the tank.
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Re: Find the length of the tank

Postby Guest » Thu Feb 20, 2014 8:02 pm

I assume if possible no wastage of steel plate.

Let W equal width of tank and 2W is the length and depth is ( W - 4 )

Base is ( W x 2W )
Sides 2 off them....( 2W x (W-4) )
Ends 2 of them.... ( W x (W-4)
The 2 ends can be made from same size as sides but cut in 2 pieces.

So... need a sheet of plate ( 2W x ( 4W - 12 ) )

and the area we are told of this is 1440 m^2.

So..... 8W^2 - 24W - 1440 = 0 .....solve for W

So...... W^2 - 3W - 180 = 0

Factorises.... ( W + 12 ) ( W - 15 ) = 0

So...... W - 15 = 0 .....So ..... W = 15


So size of plate is 30 x 48 = 1440 m^2

Size of tank is....15m x 30m x 11m = 4950 m^3

So it all works out evenly and no wastage..........


...................Simple...................
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Re: Find the length of the tank

Postby AlanAnderson » Wed Dec 03, 2014 7:04 am

Nice solution, thanks for answering.

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Re: Find the length of the tank

Postby leesajohnson » Thu Jan 12, 2017 5:01 am

4950 m^3

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