increase by 120%

[Ju1ian]

Hi,

Someone said the value of his property had increased by 120%. Literally, does this mean:

A. What used to be $100 is now $120.
or
B. What used to be $100 is now $220.
?

Apparently, the former is what he actually intended to say,
but I think the latter is what the sentence literally means. So I think he should have said, "The value has increased by 20%".
Am I getting this correct?

[Barb_D]

You are completely correct.

100 to 120 is an increase of 20%
100 to 200 is an increase of 100%
100 to 220 is an increase of 120%

[tedtmc]

You are correct.

This is nothing to do with English. Simple maths:
increase = new value - original value = $120 - $100 = $20 (20%)

[corum]

Be cautious.

$140 - $120 = $20 (≠20%)

[Ju1ian]

I agree with tedtmc that this is nothing to do with English. How come people who speak bad English are also poor at math? ...Just kidding!
Thank you all.

[corum]

How come people who speak bad English are also poor at math? ...Just kidding!

Truants. I am more surprised when I see someone who has good English and good math.

[Tdol]

I agree with tedtmc that this is nothing to do with English. How come people who speak bad English are also poor at math? ...Just kidding!
Thank you all.

Try this poll to see how good we are at maths: Poll: Operating profits have increased twofold. - Language Polls - UsingEnglish.com

[corum]

Try this poll to see how good we are at maths: Poll: Operating profits have increased twofold. - Language Polls - UsingEnglish.com

When you set about solving a mathematical problem, first you have to make sure you you understand what you read. This is very important. I think most of the voters failed to answer the question correctly because they do not know the meaning of "increase twofold". 'Increase' means the value of profits grew. If I translate 'Increase' into mathematics, it means the result will be positive. End of story. Twofold means the value of profits was X before and 2x after.
(x2-x1)/x1 is the formula we can apply to calculate the change in percentage. How does the formula work? We have to substitute the information we have translated into mathematics for the running values. Let us do this:

(2x-x)/x = 1 = 100/100 = 100%

There is no good mathematician without good reading comprehension, but this of course does not mean that your English is cool, so your math is cool too.