Multiplication error

I noticed that Excel 2003 calculates:
7.5*1.2=8.7 when the correct answer is 9.0. It did this as part of a
formula where the 1.2 answer came from calculating another set of numbers.
When I asked Excel to calculate this answer by simply inputting those two
numbers the correct answer of 9.0 came out. Does anyone have an answer as to
why it does that?!

Hmmm.... 8.7. Well, 7.5+1.2=8.7. Are you sure there's not a plus sign in
there?
*******************
~Anne Troy

www.OfficeArticles.com


"DeeJay" <DeeJay@discussions.microsoft.com> wrote in message
news:72EA8922-F5BA-4862-BECF-1039B61A1BED@microsoft.com...
> I noticed that Excel 2003 calculates:
> 7.5*1.2=8.7 when the correct answer is 9.0. It did this as part of a
> formula where the 1.2 answer came from calculating another set of numbers.
> When I asked Excel to calculate this answer by simply inputting those two
> numbers the correct answer of 9.0 came out. Does anyone have an answer as
to
> why it does that?!

On Tue, 19 Jul 2005 21:17:01 -0700, DeeJay wrote:
>I noticed that Excel 2003 calculates:
>7.5*1.2=8.7 when the correct answer is 9.0. It did this as part of a
>formula where the 1.2 answer came from calculating another set of numbers.
>When I asked Excel to calculate this answer by simply inputting those two
>numbers the correct answer of 9.0 came out. Does anyone have an answer as to
>why it does that?!

Decimal operations in the number from which one of your final
multipliers are derived?

MP-
--
"Learning is a behavior that results from consequences."
B.F. Skinner

The cell that contains 1.2 is probably rounded.

Select the cell, and click the Increase Decimal button on the toolbar.
Perhaps you'll see that it's 1.16

DeeJay wrote:
> I noticed that Excel 2003 calculates:
> 7.5*1.2=8.7 when the correct answer is 9.0. It did this as part of a
> formula where the 1.2 answer came from calculating another set of numbers.
> When I asked Excel to calculate this answer by simply inputting those two
> numbers the correct answer of 9.0 came out. Does anyone have an answer as to
> why it does that?!


--
Debra Dalgleish
Excel FAQ, Tips & Book List
http://www.contextures.com/tiptech.html

DeeJay wrote:
> I noticed that Excel 2003 calculates:
> 7.5*1.2=8.7 when the correct answer is 9.0. It did this as part of a
> formula where the 1.2 answer came from calculating another set of numbers.
> When I asked Excel to calculate this answer by simply inputting those two
> numbers the correct answer of 9.0 came out. Does anyone have an answer as
> to why it does that?!

In a word, round-off error. (Okay, that's two or threee words.)

The "1.2" that you see in some cell is not really 1.2.
It is probably close to 1.16. Format that cell with
6 or so decimal places, and you will see what I mean.
And by the way, the "8.7" is probably not 8.7.

If you want "1.2" to actually be 1.2, there are a couple
ways to make that happen. The "best" way is to change
the formula that results in "1.2" to =ROUND(formula,1).

Alternatively, there is a Tools / Options / Calculation
option to cause this for all calculations. But because
the affects the entire spreadsheet, it can have unexpected
consequences.

As you have stated that the 1.2 comes from another calculation it is likely
that the result of that calculation is actually something like 1.16. Excel is
displaying the number as 1.2 as you have the cell format set to show just one
decimal place. Try increasing the number of decimal places and see if it
makes more sense.

Hope this helps
Rowan

"DeeJay" wrote:

> I noticed that Excel 2003 calculates:
> 7.5*1.2=8.7 when the correct answer is 9.0. It did this as part of a
> formula where the 1.2 answer came from calculating another set of numbers.
> When I asked Excel to calculate this answer by simply inputting those two
> numbers the correct answer of 9.0 came out. Does anyone have an answer as to
> why it does that?!

"Anne Troy" wrote:

> Hmmm.... 8.7. Well, 7.5+1.2=8.7. Are you sure there's not a plus sign in
> there?
> *******************
> ~Anne Troy
>
> www.OfficeArticles.com
>
>
> "DeeJay" <DeeJay@discussions.microsoft.com> wrote in message
> news:72EA8922-F5BA-4862-BECF-1039B61A1BED@microsoft.com...
> > I noticed that Excel 2003 calculates:
> > 7.5*1.2=8.7 when the correct answer is 9.0. It did this as part of a
> > formula where the 1.2 answer came from calculating another set of numbers.
> > When I asked Excel to calculate this answer by simply inputting those two
> > numbers the correct answer of 9.0 came out. Does anyone have an answer as
> to
> > why it does that?!
>
>
I am sure it doesn't have a plus sign.

"Mangus Pyke" wrote:

> On Tue, 19 Jul 2005 21:17:01 -0700, DeeJay wrote:
> >I noticed that Excel 2003 calculates:
> >7.5*1.2=8.7 when the correct answer is 9.0. It did this as part of a
> >formula where the 1.2 answer came from calculating another set of numbers.
> >When I asked Excel to calculate this answer by simply inputting those two
> >numbers the correct answer of 9.0 came out. Does anyone have an answer as to
> >why it does that?!
>
> Decimal operations in the number from which one of your final
> multipliers are derived?
>
> MP-
> --
> "Learning is a behavior that results from consequences."
> B.F. Skinner
>Yes it does.

"joeu2004@hotmail.com" wrote:

> DeeJay wrote:
> > I noticed that Excel 2003 calculates:
> > 7.5*1.2=8.7 when the correct answer is 9.0. It did this as part of a
> > formula where the 1.2 answer came from calculating another set of numbers.
> > When I asked Excel to calculate this answer by simply inputting those two
> > numbers the correct answer of 9.0 came out. Does anyone have an answer as
> > to why it does that?!
>
> In a word, round-off error. (Okay, that's two or threee words.)
>
> The "1.2" that you see in some cell is not really 1.2.
> It is probably close to 1.16. Format that cell with
> 6 or so decimal places, and you will see what I mean.
> And by the way, the "8.7" is probably not 8.7.
>
> If you want "1.2" to actually be 1.2, there are a couple
> ways to make that happen. The "best" way is to change
> the formula that results in "1.2" to =ROUND(formula,1).
>
> Alternatively, there is a Tools / Options / Calculation
> option to cause this for all calculations. But because
> the affects the entire spreadsheet, it can have unexpected
> consequences.
>

Thank you- I will do that and see what happens. Thanks for the answer!