# Does the following make sense to you:

1. Jul 11, 2012

### NotAnEngineer

"expressing a reduction, as a percentage of the total amount"

I.e...

If I have 20 of 100 items then I have 20%.

If I reduce that number to 15 then I would have 15%.

That would be a reduction of 5 items, or a 25% reduction%.

OR

a reduction of 5% of the total amount

EDIT: this is not a trick, or some mind game. just take the original phrase at face value. If someone said to you "Im going to express the reduction/addition, as a percentage of the total amount" does that make sense to you??

Im just trying to get a general feel that if I express something like that, would the average "math" person pick up on what I said?

Last edited by a moderator: Jul 11, 2012
2. Jul 11, 2012

### sambarbarian

yes , yes it does make sense

3. Jul 11, 2012

### A.T.

OR

a reduction by 5pp (percentage point)

http://en.wikipedia.org/wiki/Percentage_point

4. Jul 11, 2012

### pgardn

Here is where statements can get one into trouble if not expressed fully in some understandable manner. This reminds me of math problems that come out wrong due to language and are used as lessons. I recall some tricky wording with a hotel and rates.
Imo this is horribly worded. I often catch myself doing the same thing.

My first problem:

If I reduce that number to 15... Are you now only choosing 15 out of the original 100? Or have you actually taken out removed 5 items of the original 20 so that we now have 15 out of 95?

5. Jul 11, 2012

### NotAnEngineer

Yes, that is another way to express it, but does "reduction, as a percentage of the total amount" make sense to you?

6. Jul 11, 2012

### NotAnEngineer

How would you word it??

7. Jul 11, 2012

### sophiecentaur

That statement doesn't make it clear what is meant without adding the rest of the story. It is a 'bad' use of the maths. It's true that the 5 items represent 5% of the original 100 and it's true that 5 items represent 25% of the 20 - but so what??? The statement is not actually wrong but what sense is there in making it?
Percentages, used more than once in an argument need to be treated with care because people often try to pull a fast one that way.

Multiple 'percentage' reductions should be dealt with correctly, that is by multiplication.
Thus, 20% off then another 10% off is 0.8 X 0.9 (=0.72) or 72%, which means 28% overall reduction and not 30%.

8. Jul 11, 2012

### NotAnEngineer

just to simply express a reduction. Does it makes sense to you talk about the reduction in terms of a percentage of the total amount? If it is specified like that of course.

This is just talking about a single percentage reduction, not multiple.

i.e.
a reduction of 5pp
a reduction of 25%
a reduction of 5% of the total

9. Jul 11, 2012

### pgardn

Now lets choose 15 out of the original 20. So that would be 15 out of 100 or 15%

10. Jul 11, 2012

### Naty1

"Figures don't lie but liars figure."

11. Jul 11, 2012

### NotAnEngineer

Okay, I said that much.

Go on...

12. Jul 11, 2012

### sophiecentaur

The fact that you are needing to query it means that the statements could probably be made in a better way and are open to misunderstanding. What is the point of all that preamble if the information is that the five in your hand represent 5% of the original. Are they a "reduction"? I don't see how; they are just five items. What about the other 15 items, of the 20 that were originally taken out? Are they then put back, amongst the 80 still on the shelf? The scenario is a bit baffling.

What would be the purposes of stating the situation in the two different ways? To give information or to cloud the situation?

13. Jul 11, 2012

### pgardn

No actually I did not get that from the original statements.

14. Jul 11, 2012

### pgardn

Then, and this may be my problem, I have no idea what a reduction percentage is.

15. Jul 11, 2012

### NotAnEngineer

I think there are many ways to express it, and as to which one is better, that is an opinion.

Im just trying to figure out if the general idea of expressing a reduction, as a percentage of the total, makes sense to you.

You're thinking about it too much. Again, I really just asking if the general idea of expressing a reduction, as a percentage of the total, makes sense to you.

16. Jul 11, 2012

### sophiecentaur

The way figures are presented can be shameless. "Five times less pollution" - wtf? What's wrong with "One fifth of the pollution"?

17. Jul 11, 2012

### NotAnEngineer

"If I reduce that number to 15 then I would have 15%"

i.e. 15 out of 100

Regardless, does the idea of expressing a reduction, as a percentage of the total amount, make sense to you??

18. Jul 11, 2012

### NotAnEngineer

The phrase "reduction percentage" was never used.

This is referring to phrase "reduction, as a percentage of the total amount"

19. Jul 11, 2012

### sophiecentaur

It's the way prices are advertised in shop windows so I am used to it. I wouldn't like to see it used in a scientific argument except, perhaps, in a summary. Bearing in mind how few people actually understand percentages (this is true) then I would say many people are duped when information is presented in those terms.

20. Jul 11, 2012

### pgardn

That would be a reduction of 5 items, or a 25% reduction%.

My bad I guess. What is the bolded?