%

[Homer55]

How do you work out a percentage on a calculator.

I say to take 30% off something you divide it by 1.30.

but somebody else says you just minus 30 and press the % button? can anyone help

[jake-the-peg]

Your friend is right you have to subtract 30% of the original

You could do it by multiplying by 0.7 that is the same as dividing by about 1.429 not 1.3


What is 30% off of 100? 70 right?

but 100 divided by 1.3 is about 76.9

[Homer55]

What about adding %, can you multiply by 1.30?

[JudgeJ]

Forget your calculator for a minute and try to understand what you are doing.

A percentage of something is simply a fraction expressed in terms of a hundred. So 50% is a half, or 0.5, multiplied by 100.

To take an example, 15 is a half of 30. To calculate this as a percentage divide 15 by 30 (=0.5) and multiply the result by 100 = 50%. So 15 is 50% of 30.

The example you quoted seeks to reduce a number by a percentage. To reduce 30 by 30% you have to firstly calculate 30% of 30 (=30 x 0.3 =9) and deduct the answer from 30. (30-9=21). So 30, reduced by 30% is 21.

If you adopted your suggested process of dividing by 1.3 you would arrive at 23.07. (try it and see). If you adopted your friend�s suggestion you would end up with zero. (30-30=0 and pressing the �%� key would still result in 0.

Some calculators have a �Mark Up� and �Mark Down� function where you would simply key in �30� �X� �30� �%� and �Mark Down� to get the answer 21. Otherwise you have to do the calculation in two stages as I described.

On a standard calculator all that pressing the �%� key does is to divide the answer by100. Pressing �30� �X� �50� would normally give you the answer 1500 if you pressed the�=� key. Pressing the �%� key reduces it to 15.

It is always best to understand what you are setting out to do before hitting the keys on the calculator!

[jake-the-peg]

Sorry I don't think I explained it very well

Yes you can increase by 30% by multiplying by 1.3.

but if you're subtracting a percentage it's best to use the 2 stage approach

[fo3nix]

Personally I find it easier to forget the percentage sign button altogether, and just think in decimal.

1% is 0.01
10% is 0.1
100% is 1
60% is 0.6
etc.

So say you have something worth �5. 60% of this is 5x0.6 = �3.

If you need to add a percentage, then just remember that 120% will be 1.2, etc. So if your item is �7, adding 30% to the price is the same as multiplying by 1.3, which will give 7x1.3 = �9.10

[Homer55]

thanks guys

[Bazile]

I do a lot of number crunching at work and use a casio calculator - which calculates percentages as simple as follows :-

e.g 80 minus 30 % -
(a) tap in 80
(b) tap in x 30 then hit % button
(c) then hit minus button

e.g 80 plus 30 %
same as above but at ( c ) - you hit the plus button

only works on casio calculators , for some reason
Is anyone else aware of the above ?