# Am I wrong or is the textbook wrong?Watch

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#1
I was helping someone I know out with a Maths question, but it seemed as if the textbook gave a different answer to the question than to the one we both got. Here is the question and all my working:

A rectangular prism has a square base m and volume .

(i) Find an expression, in terms of x, for the height of the prism.

(ii) Hence, find the surface area of the prism.

The area of the prism's cross section is going to be: , which means that it is

The area of the base of the prism is:

The prism's other face is also equal to , so its area is too.

Which means that the total surface area of the prism is going to be all of those added together and multiplied by 2, hence the surface area is:

. However the textbook says that the answer is

So have I done something wrong or is the textbook wrong?

*Sorry for the incorrect use of the = sign; I didn't know how to get the identical sign with LaTex.

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5 years ago
#2
(Original post by kingaaran)
I was helping someone I know out with a Maths question, but it seemed as if the textbook gave a different answer to the question than to the one we both got. Here is the question and all my working:

A rectangular prism has a square base m and volume .

(i) Find an expression, in terms of x, for the height of the prism.

(ii) Hence, find the surface area of the prism.

The area of the prism's cross section is going to be: , which means that it is

The area of the base of the prism is:

The prism's other face is also equal to , so its area is too.

Which means that the total surface area of the prism is going to be all of those added together and multiplied by 2, hence the surface area is:

. However the textbook says that the answer is

So have I done something wrong or is the textbook wrong?

*Sorry for the incorrect use of the = sign; I didn't know how to get the identical sign with LaTex.

Posted from TSR Mobile
Double check the question - if this is a solid prism then you are, of course, correct
0
5 years ago
#3
(Original post by kingaaran)
I was helping someone I know out with a Maths question, but it seemed as if the textbook gave a different answer to the question than to the one we both got. Here is the question and all my working:

A rectangular prism has a square base m and volume .

(i) Find an expression, in terms of x, for the height of the prism.

(ii) Hence, find the surface area of the prism.

The area of the prism's cross section is going to be: , which means that it is

The area of the base of the prism is:

The prism's other face is also equal to , so its area is too.

Which means that the total surface area of the prism is going to be all of those added together and multiplied by 2, hence the surface area is:

. However the textbook says that the answer is

So have I done something wrong or is the textbook wrong?

*Sorry for the incorrect use of the = sign; I didn't know how to get the identical sign with LaTex.

Posted from TSR Mobile
use * or \times() to denote the multiplication operation. Equivalent is \equiv"".
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#4
(Original post by keromedic)
use * or \times() to denote the multiplication operation. Equivalent is \equiv"".
Okay, thank you very much!

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#5
(Original post by TenOfThem)
Double check the question - if this is a solid prism then you are, of course, correct
The question says that it is an "open rectangular bank"
0
5 years ago
#6
(Original post by kingaaran)
The question says that it is an "open rectangular bank"
Then it does not have a "top" hence the missing

Did it ask for the external surface area
0
#7
(Original post by TenOfThem)
Then it does not have a "top" hence the missing

Did it ask for the external surface area
Oh, I understand now! (facepalm) No, it just said work out the surface area. Thank you

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