Simple Maths

[Supernick]

I've finally accepted that I can't do what appears to be basic Maths, and have found out that everyone in my immediate surroundings is the same. Quite what this says about us is worrying, but I thought I'd throw it open to a wider, more knowledgeable audience. I want to write an excel formula for this maths.

There are 2 totals - A and B, and they represent 2 figures from 2 weeks of information. B is higher than A, and I want to show what % increase there was from week to week. Go!

[banth]

I think you divide the difference of the two by the smaller number then multiply by 100.

I.e. if A is 8 and B is 10 then:

difference is 2 (from 10 minus 8), divided by 8 is 1/4, multiply by 100 is 25%.

In this example, B is 25% larger than A.

Is that what you were looking for?

If I have it wrong I apologise, not done maths for a while!

[Hippy]

In thje answer cell you type:

=(B/A%)-100

where A and B are the cell definitions =(C4/B4%)-100 for eaxample. This takes this week's total and finds the percentage increase or decrease from the previous week's total. If this week happened to be less then you would get a minus percentage, showing the percentage decrease.

Simple, eh?

[Loosehead]

Or ((B-A)/A)x100

[pilotlight]

Sorry, Maths and Arithmetic were my 3 worst subjects at school!

[JudgeJ]

Yes, Hippy and Loosehead have emphasised the important point.

You do not necessarily divide by the smaller number. You must divide by the base number (that is, the number upon which you are making the comparison). If you want to calculate week on week difference, the week 2 reading may actually be lower than the week 1 reading.

So, the formula is:

(Week2 ) minus (Week1)

Divide this answer (which may be a negative value) by Week 1.

Multiply the answer by 100 (to make it a percentage).

Two examples:

Week 1 = 8, Week 2 = 10

(10-8) = 2

2 Divided by 8 =0.25 (multiplied by 100 = 25%)

Week 1 =10, Week 2 = 8

(8-10) = -2

-2 Divided by 10 = -0.2 (multiplied by 100 = -20%)