Susan Welsh (asker) Jan 22, 2015:

@Rachel @Amy Thanks, that is helpful. "decreased by a factor of 2.2" even gets ...114,000 Google hits, so who can go wrong?!
Amy, please put up an answer or the system will nag me forever to close the question.

Rachel Douglas Jan 21, 2015:

by a factor of 2.2 (or by ~55%) Amy gave the answer, so maybe she'll post it. I find it helps to replace "by X times" with "by a factor of." If something is reduced "by a factor of 3," that means it's reduced to 1/3 or by 2/3. If it's reduced "by a factor of 2.2," it's reduced to 45% or by 55% (rounding), as has been said. You get the "45" by dividing 1 by 2.2 = 0.45... Then, if you need to determine the initial value, the arithmetic for your case of an outcome value of 3, is x is to 3 as 100 is to 45. Answer: (about) 6.6666666666666666666666666... (6 and 2/3). (That is, x/3 = 100/45; so 45x = 300; x = 300/45.)

The Misha Jan 21, 2015:

Taking what GaryG said a step further, unless it is some kind of technical drudgery that requires precision in numbers, I don't see anything wrong with saying they cut it in half, give a take, which is just about right and it's better English too. No one really cuts it by 54.54%.

Susan Welsh (asker) Jan 21, 2015:

thanks I'm feeling both linguistically and arithmetically challenged by this one!

Amy Lesiewicz Jan 21, 2015:

The final value of 3 tons is 45.45% of the initial value of 6.6 tons. So you could say "reduced by 54.54%" (or round that up to 55%).

Amy Lesiewicz Jan 21, 2015:

"Reduced by 33%" to me means 33% less, or X minus 33% of X. In our example, this would be 6.6 - (6.6/3) = 6.6 - 2.2 = 4.4.

GaryG Jan 21, 2015:

Per Google's calculator: 1 / 2.2 = 0.454545455

Susan Welsh (asker) Jan 21, 2015:

@Gary and Amy So I guess we would say in English...
reduced by 33%

GaryG Jan 21, 2015:

сокращение в 2 раза would be "halved", so think of X being multiplied by 1/2.2