Need a formula

[Serena]

I have been working as an Elementary computer teacher. I was recently
promoted to teaching MS/HS... I have been busy this summer creating lesson
plans and I have more to learn about Excel & formulas. I want to teach the
students how to use a particular chart. I have the top 10 countries that
import from the U.S. I have the $ amounts for each country. Canada imported
211.9 billion in 2005, which is up 31.7% from 2002. What is the formula to
figure out the amount in 2002? I know that on the news I will hear that a
certain stock is up _______ % from yesterday. I could forego this, but
believe that this is very important to teach. Algebra was NOT my strong
suit. My husband came up with a formula, but neither of us know how to write
it into Excel. I need to understand it, so that I can teach it. Your help
is greatly appreciated!
-Serena-

 

[FSt1]

hi
excel see a percent as a decimal of 1. so excel see 31.7% as .317.
=211.9*(1-.317)
or 144.7 which is 68.3 % or .683(1-.317) of 211.9.
if 211.9 was in B2 and 31.7% was in c2 then the formula could look like this.
=B2*(1-C2)
c3 would be enter as .317 then formated to percent to look like 31.7%
formating does not change the value, it only changes the way it looks.

regards
FSt1

 

[Pete_UK]

In your example, 211.9 billion is 131.7% of the 2002 figure, so the
2002 figure is 211.9 / 1.317.

In Excel, if you put 211.9 in cell A1 and 31.7% in cell B1, then in C1
you could have this formula:

=A1/(1+B1)

Hope this helps.

Pete

 

[Bernard Liengme]

Let's say the 2002 figure was X
2003 figure + increase = 2005 figure
X + X*31.7% = 211.9
X(1+31.7%)=211.9
X(1+31.7/100)=211.9
X= 211.9/(1.317)
X=160.9

In Excel:
Let A1 have the value 211.9, B1 the value 31.7%
In C1 use formula =A1/(1+B1)

Note that Excel might give 160.896 must you must rounf this to 1 place of
decimal since you know the 2005 figure only to 1 place of decimal (its all
about significant figures as your physics teachers will tell you)
best wishes

 

[JoeU2004]

Canada imported 211.9 billion in 2005, which is up 31.7% from
2002. What is the formula to figure out the amount in 2002?

The algebra is elementary, literally; most of MS/HS will already know this:
211.9 billion is (1+31.7%) times what?

211.9 = (1 + 31.7%) * A1

A1: =211.9 / (1 + 31.7%)

You need to remember that A1 is expressed in term of billions of dollars.


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