How do I get a true calculation?

[Guest]

Hi. I think I have just posted this question, but I can't find it now, so my
apologies.....
I need to start at number 1 and multiply it by 2 - then multiply that answer
by 2, then multiply that answer by 2 and carry on until I have done that 480
times!!
when I try to do this in excel, I either get the answer 4.72237E+21 (which
means nothing to me) or £4,722,366,482,869,650,000,000.0 which isn't a true
calculation as I have worked it out up to a point, but I dont have enough
spaces on my calculator. Bearing in mind that I have not used excel since I
last worked (about 3 years ago), answers as simple as possible please.
Thanks

 

[Niek Otten]

So what you require is 2 to the power of 479 or 480?
Your result is 2^408, not 2^480.

--
Kind regards,

Niek Otten


--
Kind regards,

Niek Otten

| Hi. I think I have just posted this question, but I can't find it now, so my
| apologies.....
| I need to start at number 1 and multiply it by 2 - then multiply that answer
| by 2, then multiply that answer by 2 and carry on until I have done that 480
| times!!
| when I try to do this in excel, I either get the answer 4.72237E+21 (which
| means nothing to me) or £4,722,366,482,869,650,000,000.0 which isn't a true
| calculation as I have worked it out up to a point, but I dont have enough
| spaces on my calculator. Bearing in mind that I have not used excel since I
| last worked (about 3 years ago), answers as simple as possible please.
| Thanks
|

 

[Niek Otten]

Sorry, little mistake, your result is 2^72.

--
Kind regards,

Niek Otten

| So what you require is 2 to the power of 479 or 480?
| Your result is 2^408, not 2^480.
|
| --
| Kind regards,
|
| Niek Otten
|
|
| --
| Kind regards,
|
| Niek Otten
|
|| Hi. I think I have just posted this question, but I can't find it now, so my
|| apologies.....
|| I need to start at number 1 and multiply it by 2 - then multiply that answer
|| by 2, then multiply that answer by 2 and carry on until I have done that 480
|| times!!
|| when I try to do this in excel, I either get the answer 4.72237E+21 (which
|| means nothing to me) or £4,722,366,482,869,650,000,000.0 which isn't a true
|| calculation as I have worked it out up to a point, but I dont have enough
|| spaces on my calculator. Bearing in mind that I have not used excel since I
|| last worked (about 3 years ago), answers as simple as possible please.
|| Thanks
||
|
|

 

[Guest]

I need to start at number 1 and multiply it by 2 - then
multiply that answer by 2, then multiply that answer by
2 and carry on until I have done that 480 times!!

That can be written =2^480 in Excel, which reads "2 to the
power of 480".

when I try to do this in excel, I either get the answer
4.72237E+21 (which means nothing to me)

It means "4.72237 times 10 to the 21" -- that is, 472237
followed by 16 zeros. It is called scientific notation. If you
change the format to Number (Format > Cells > Number >
Number, you will see something closer to what you expect.

But that is 4.72237E+21 2^72, not 2^480. 2^480 is closer
to 3.1217E+144.

or £4,722,366,482,869,650,000,000.0 which isn't a true
calculation as I have worked it out up to a point, but I dont
have enough spaces on my calculator.

And just like your calculator, Excel -- and all computational
devices -- have a limit to the "space" in which they can
represent a number. Some calculators simply give up beyond
that. Excel does its best by showing numbers in scientific
notation, by default. But even if you use the Number format,
only the first 15 non-zero digits are accurate, more or less.
(The 15th digit might be rounded.)

answers as simple as possible please.

Hope that's simple enough.

And to answer your question ("how do I get a true calculation"),
there are multiprecision arithmetic add-ins that claim to have
more accuracy. I have not personal experience with any of them.