UKC

So

if something used to take 80 days to complete, and now only takes 20, what % improvement is this?

if it was down to 40%, I think it would be a 100% improvement, so is down to 20 days a 200%, or maybe 400% improvement???

Mick

In reply to Mick r:


It is a 75% decrease in time if that's what you mean.

In reply to Robert Durran:

thanks but what about improvement?

In reply to Mick r:

It's a 75% reduction in time taken or a 400% improvement .

In reply to Mick r:


You need to define percentage improvement if you insist on it being something other than percentage reduction. You seem to want it to be the percentage increase which would reverse the percentage reduction.

In reply to Mick r:





Rephrasing it, you can now do 4 of something in 80 days rather than just 1 of it, so you've improved by 3, which is 300% of your earlier performance. It can't be 400% because that would mean an improvement of 50% would actually be a decrease.

In reply to Mick r:

Well its four times faster so the speed of completion is 400% because on that scale 80 days = 100% of the time.

But the percentage of improvement means 80 days represents a 0% improvement, so 40 days would be a 100% improvement and 20 days 200%.

In reply to Mick r:

Productivity is 400% what it was before.

In reply to Lord_ash2000:



If you improve your speed by 200% you'll go 3 times as fast, by 300% you'll go 4 times as fast, etc., but your final few words claim that a 200% speed improvement will make you 4 times as fast (and by presumed extension a 300% speed improvement will make you 8 times as fast, etc.) I don't see where the logarithmic element comes from.

Instead of "80 days represents a 0% improvement, so 40 days would be a 100% improvement and 20 days 200%" I would write "80 days represents a 0% improvement, so 40 days would be a (80/40)-1 = 100% improvement and 20 days (80/20)-1 = 300%

In reply to Mick r:
The discussion on this thread is one reason why many pupils are turned off maths and why some pupils find the subject fascinating.

In reply to Mick r:

Eighty days is a quarter and a bit of a year, so if it was a slope each month would be 1 in 12. Eighty days is therefore 3 in 12, give or take, or a quarter, which is a slope of 25%, and if it's 4 times less than that then it's now 6.25%.

So it's a 6.25% improvement, which ain't great to be honest. Perhaps you're not giving it your all?

In reply to felt:
Except a 1:1 gradient is only 45 degrees, it's not vertical. You're comparing apples and clothes pegs, which even I can see isn't appropriate!

Edit: I should I'd say it's a 200% improvement by my [no doubt faulty] reckoning.

In reply to Mick r:
Improvement isn't a mathematical term and it just creates an ambiguous metric. Robert Durran's 75% decrease in time or a statement along the lines of, "The operation is now completed is a quarter of the time" is accurate and easily understood, %age improvement is always ambiguous.

In what context do you wish to use this?

In reply to Mick r:

It's a million percent. We're in a post-truth era.