Math question

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JulianMathHelp

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If the dimensions of something is enlarged by 400%, then is the new shape 400% of the old shape, or 400% bigger than the old shape?
 
So if the area of the old shape is 5, and the shape is enlarged by 400%, then does that mean the new shape is 5x as big as the old ship, meaning the new area is 125?
 
JulianMathHelp said:
So if the area of the old shape is 5, and the shape is enlarged by 400%, then does that mean the new shape is 5x as big as the old ship, meaning the new area is 125?
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5x is correct. Are you sure about 125?
 
This is the problem I was looking at:
Mr. Wallis took his home design to the copier and enlarged it 400%. What is the area of the diagram now? Show how you know.
Does the word "by" make a difference? This is because I checked the answer key and it said that it meant "4x as large". So now I'm not sure which to go to.
 
JulianMathHelp said:
This is the problem I was looking at:
Mr. Wallis took his home design to the copier and enlarged it 400%. What is the area of the diagram now? Show how you know.
Does the word "by" make a difference? This is because I checked the answer key and it said that it meant "4x as large". So now I'm not sure which to go to.
Click to expand...
Ok, I missed the fact that you are actually talking about area measurements. Posting the original problem is always better than trying to summarize it in your own words.
"Enlarge it 400%" probably means make new linear dimensions 4 times old dimensions.
If old dimensions are A and B, old area is A*B.
New dimensions are 4A and 4B, new area: 16A*B or 16 times old area.
 
JulianMathHelp said:
So the word "by" can make a large difference, I guess I'm going to have to be careful
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Enlarge by 400% means add 400% of the original size.
Enlarge 400% is somewhat ambiguous. If it means 4*old size, then what does enlarge 50% mean? 0.5*old size is not exactly enlargement.
 
Hi Julian. Draw a rectangle with dimensions 5 units by 1 unit. If you enlarge the rectangle 400%, what are the new dimensions? How do the two areas compare?

Also, the words "area" and "shape" have different meanings, so you can't use them in English as though they mean the same thing.

?
 
Otis said:
Hi Julian. Draw a rectangle with dimensions 5 units by 1 unit. If you enlarge the rectangle 400%, what are the new dimensions? How do the two areas compare?

Also, the words "area" and "shape" have different meanings, so you can't use them in English as though they mean the same thing.

?
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That's what I was asking, I wasn't sure if that meant 400% of the old side, or 400% larger than the old side. I'm still not very clear, so if you could explain it to me that would be great :)
 
JulianMathHelp said:
… wasn't sure if that meant [adding] 400% [to the] side, or 400% larger …
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How are similar, worked examples worded? I agree that ambiguity is possible, but I read it to mean the new dimensions are four times bigger.

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JulianMathHelp said:
Four times bigger means 5x as large. Don’t you agree?
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To me, "four times bigger" means multiplied by 4.

As lev888 and I said, there's no consensus because people use various wordings inconsistently to mean the same thing. Do you have other worked examples, to compare wording?

At school, when I couldn't decide between two interpretations, I'd work the exercise both ways and explain why,.

JulianMathHelp said:
Sorry for asking so many stupid questions
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Don't be concerned about that.

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