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what formula do i need to calculate 75% of a number which then decreases by 90%

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what formula do i need to calculate 75% of a number which then decreases by 90% andie856603 5/20/11 10:15 AM
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Re: what formula do i need to calculate 75% of a number which then decreases by 90% Bipan Kundal 5/20/11 7:57 PM
=((A1)*75%)-((90%)*A1*75%)        where A1 is the original number
Re: what formula do i need to calculate 75% of a number which then decreases by 90% Ted J 5/20/11 9:56 PM
The formula works however I would recommend

=(A1*.75)-(.9*A1*.75)

andie856603, will your two respective percentages always be 75% and 90%?  If they change we can write you a formula that allows you type change those values and always have the correct result.

As a note, I chose the decimal forms because writing a number as a percentage is a formatting step and I generally encourage keeping numbers in calculations in the purest forms...(so one could argue for =(A1*(3/4))-((9/10)*A1*(3/4)) as well but I thought it was uglier)...

Just my opinion though...

Re: what formula do i need to calculate 75% of a number which then decreases by 90% andie856603 5/21/11 2:35 AM
thank you both for you help with this is much appreciated what i also need to do with this also is add another value...yes the original number will stay the same but where would i enter the column/row to show if it was the 1st/2nd/3rd etc calcution of this number ie 1 would be 75% of original then 2 90% of that 3 90% of 2..... 4 90% of 3 and so on
Re: what formula do i need to calculate 75% of a number which then decreases by 90% Ted J 5/21/11 8:29 AM
Try this:

Let A2 be where you type the original number. Type "Original Number" in A1 as your header
Let B2 be Calculation 1 and the formula =A2*.75.  Type "Calculation 1" in B1 as your header
Let C2 be Calculation 2 and the formula =B2*.9. Type "Calculation 2" in C1 as your header
Let D2 be Calculation 3 and the formula =C2*.9...and so on

You can copy the formula from C2 across as many times as you want by using Ctrl+C and Ctrl+V.  The copied formula will always use the cell immediately to the left and multiple it by .9.
Re: what formula do i need to calculate 75% of a number which then decreases by 90% andie856603 5/21/11 11:25 AM
o.k again thanks for helping me with this your answer it great although would it be possible in add this into the original formula rather than have extra colums so i could change the number to 1,2or 3 etc to then show 1st,2nd or 3rd calculation etc in one column?

Re: what formula do i need to calculate 75% of a number which then decreases by 90% AD:AM 5/21/11 6:53 PM
Try:

A2: original number
B2: calculation step (0, 1, 2, 3 etc)

C2:

=IF( LEN( A2 ) ; A2 * ( 0.75 ^ SIGN( B2 ) ) * ( 0.9 ^ MAX( 0 ; B2 - 1 ) ) ; IFERROR( 1/0 ) )

HTH
Adam
Re: what formula do i need to calculate 75% of a number which then decreases by 90% Yogi Anand 5/21/11 8:37 PM
Hi Andrea: 

I believe you and I have worked on this problem or a very similar one before. In any event, 
I have used the following formula ...
=ArrayFormula(if(C:C,StartingNumber*x%*y%^(row(C:C)-1),iferror(1/0)))

as shown in the illustration for you in my Blog on 
Cloud Computing -- Google Docs Way
yogi_calculate X Percent Of A Number Which Then Is Successively Decreased By Y Percent

Please check it out to see how this works for you.

Cheers!
Yogi


Re: what formula do i need to calculate 75% of a number which then decreases by 90% andie856603 5/22/11 7:22 AM
hi yogi yes you have helped me before & your formula works perfect for me as i am expanding my game i am adding additional data to my spread sheet this calculation is very complex perhaps you would like me to share the sheet with you then i can explain more

Re: what formula do i need to calculate 75% of a number which then decreases by 90% andie856603 5/23/11 12:24 PM
thank you problem solved :o)