[General] increase of twofold and 200%

Dear teachers

Is th use of "twofold" correct in sentence 1)? In sentence 2), shall I use 100% or 200%. If 200% is correct in 2) is correct, then a 100% in salary will be no increse?


1) My bank account balance increases by twofold from $100 to $200.
2) My bank account balance increases by 100%/200% from $100 to $200.


Regards

Anthony the learner

I think most native speakers would put it more simply:

'My bank balance doubled last year to $200.'

patran said:

Is th use of "twofold" correct in sentence 1)? In sentence 2), shall I use 100% or 200%. If 200% is correct in 2) is correct, then a 100% in salary will be no increse?


1) My bank account balance increases by twofold from $100 to $200.
2) My bank account balance increases by 100%/200% from $100 to $200.

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Wherever the word “increase” (or decrease, or more/less) is used, the “percent change” should be used. People get this confused though, and will sometimes use the ratio.

Therefore, 1) is incorrect, but I can see someone saying it.

For 2), the correct answer is 100%, but again, you will hear people (incorrectly, IMO) say “an increase of 200%”. To use “200%” in this case, you’d have to state it something like “My bank account balance is now 200% of what it was last year.”