A student wants to purchase a wallpaper border for a bedroom......

eddy2017

eddy2017

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Hi,
A student wants to purchase a wallpaper border for a bedroom. The border is sold in rolls 8 yards long and 10 inches wide. The room measures 12 feet by 13 feet. By performing the following operations, the student determines that 6 rolls of border are needed.

Which statement best explains the student's mathematical error?

Choose an answer
  1. The student rounded incorrectly and thought only 6 rolls were needed.
  2. The student found the perimeter instead of the area of the room.
  3. The student did not change all of the dimensions to the same units.
  4. The student used an incorrect formula for perimeter.

I tried to find out something about the area and go from there. I am not sure that is okay. You will be the judge of that.
I decided to convert everything to inches, so I am left with a wallpaper border roll in inches.

roll 288 in * 10 in

And then taking the room dimensions from feet to inches : 144 in * 156 in

I guess I should then find the area of the room

A= l * w

A=22464 in^2 -------------this is the size of the room in inches

Now I have a question as to how from this information I can figure out how many rolls of wallpaper border I need (assuming what I did is correct).
thanks for any hint,
eddy
 
I guess we should assume that the border will be 10 inches wide and that the room is rectangular. How far around the room is it? Remember you are just putting wallpaper along the border of the room and it will be 10 inches wide (the border is the very bottom of each wall). How long of a sheet of wall paper that is 10 inches wide does she need?
 
I think instead of the area I should have found the perimeter. I'll do that tomorrow, Mr Jomo. I need a break now. It is been a good math day!
thanks to all of you!!
 
I'm sorry. I forgot to write the operation the student performed. This comes with the problem.
2(13+12)/8 =6.25
 
I think, after taking a good look at this, that the student used different units. Did not convert the different measures given into a single unit.
That is why he gets 6.25
 
eddy2017 said:
The student rounded incorrectly and thought only 6 rolls were needed.
Click to expand...
Then you say:
eddy2017 said:
That is why he gets 6.25
Click to expand...
6.25 rolls will be required - which HAS TO BE rounded up to 7 rolls, for practical reason . .............................Incorrect - the amount of paper in a roll is 24 ft - i.e. - wall paper length in a roll is 8 yds (= 24 ft)
 
Last edited by a moderator:
No, I started to write the choices given after posting the operation he performed.
Which statement best explains the student's mathematical error?

Choose an answer
  1. The student rounded incorrectly and thought only 6 rolls were needed.
  2. The student found the perimeter instead of the area of the room.
  3. The student did not change all of the dimensions to the same units.
  4. The student used an incorrect formula for perimeter
I have to choose one of these choices.
He divides feet into yards which is incorrect. Take a look at the operation given and back at the dimensions given in the problem.
There is no conversion to either yards/ feet or inches in the operation he performed. Into only one of this.
 
Last edited:
eddy2017 said:
No, I started to write the choices given after posting the operation he performed.
Which statement best explains the student's mathematical error?

Choose an answer
  1. The student rounded incorrectly and thought only 6 rolls were needed.
  2. The student found the perimeter instead of the area of the room.
  3. The student did not change all of the dimensions to the same units.
  4. The student used an incorrect formula for perimeter
I have to choose one of these choices.
He divide feet into yards which is incorrect. Take a look at the operation given and back at the dimensions given in the problem.
There is no conversion to either yards/ feet or inches in the operation he performed. Into only one of this.
Click to expand...
@Subhotosh Khan is giving you a hint to one of the answer choices.
 
Jomo said:
What units go with 2(13+12)?
What units go with
Click to expand...
I had been eliminating the choices.
Eg, he found the perimeter. He applied the formula. We can see it from the operation
P = 2(l×w)
He multiplied the dimensions of the room 12 by 13 but he divided by 8 when the problem says the rolls are 8 yes long and 10 in wide.
This operation gave him 6.25
Error # 1 he didn't convert into a single unit.
So. Choice #3 checks out
 
The operation given in the exercise is:
2(13+12)/8
=6.25

And then he divides by 8, by the rolls are sold on 8 yards long by 10 in wide.
So how can he multiply different units?.
Hence my decision to go for choice C.
 
eddy2017 said:
I had been eliminating the choices.
Eg, he found the perimeter. He applied the formula. We can see it from the operation
P = 2(l×w) ......................................????????
He multiplied the dimensions of the room 12 by 13 but he divided by 8 when the problem says the rolls are 8 yes long and 10 in wide.
This operation gave him 6.25
Error # 1 he didn't convert into a single unit.
So. Choice #3 checks out
Click to expand...
Incorrect
 
Choice A . I don't think he rounded incorrectly. I think he performed operation.
 
I don't get it.
I did the operation myself and it gives 6.25 as a result. Rounded down here is arbitrary when you have a choice with a weightier reason.
He did not convert the units.
Now the question is: what would happened if he had converted everything to inches. It would be interesting to find out the result of that.
 
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