And the usage always seems to involve a number between 100 and 200: "a buck fifty" and so forth (the term seems to be wedded to the indefinite article: "a buck something ").
kcra.com: How to see 6 planets align in the night sky on Saturday
How to see 6 planets align in the night sky on Saturday
Forbes: See Venus Meet Uranus And The Pleiades Tonight In Naked-Eye Sky Show
See Venus Meet Uranus And The Pleiades Tonight In Naked-Eye Sky Show
MSN: 6 planets will soon be visible in the night sky. Here's how to see them.
6 planets will soon be visible in the night sky. Here's how to see them.
Add Yahoo as a preferred source to see more of our stories on Google. One of the coolest celestial events is happening this week, where six planets will be visible in the night sky at the same time.
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 ...
As you note, "percent" means "for every hundred," so there is nothing at all wrong with percent values greater than 100 when discussing proportions, e.g. profits increased by 120%. Like fractions, however, percent values are longer to express than multiples, so for values much greater than 100 you may hear them less frequently: