redsharknews.com: Panasonic announces LUMIX S 70-300mm super telephoto zoom for L-Mount cameras. There’s been one type of lens that the L-Mount lineup has been needing for a while now, and that’s a super telephoto zoom. Today Panasonic obliged with a new LUMIX S 70-300mm option.

Context Explanation

One of the ... The flow rate increases 100-fold (one hundred-fold) Would be a more idiomatic way of saying this, however, the questioner asks specifically about the original phrasing. The above Ngram search would suggest that a one hundred has always been less frequently used in written language and as such should probably be avoided. Your other suggestion of by one hundred times is definitely better than a ...

Insight Material

Yes, the correct usage is that 100% increase is the same as a two-fold increase. The reason is that when using percentages we are referring to the difference between the final amount and the initial amount as a fraction (or percent) of the original amount. Why is "a 100% increase" the same amount as "a two-fold increase"? If soap A kills 100% and soap B kills 99.99% of bacteria, the remaining amount of bacteria after applying A (0%) is infinitely smaller than the remaining amount of bacteria after applying B (0.01%). Therefore A is much, much better.

Final Conclusion

You can see from these examples that 0.01% gap behaves differently across the percentage scale. People often say that percentages greater than 100 make no sense because you can't have more than all of something. This is simply silly and mathematically ignorant. A percentage is just a ratio between two numbers. There are many situations where it is perfectly reasonable for the numerator of a fraction to be greater than the denominator. 2 Use 100% when you are stating mathematical thought like statistics.

Use "one hundred percent" when you are stating non-mathematical thought like a story.