quick help with maths question please

[bednobs]

long time ago since i was in school!
i have a bill for £600 including vat and i need to work out how much it would be exclusive of vat (at 17.5%) dont even know where to start!

[another-view]

Frightening!

Divide 600 by 1.175 to get £510.64

[Ankou]

divide the number by 1.175

[jake-the-peg]

600 divide by 117.5 multiplied by 100

[bednobs]

really frightening when you realise i used to be a palliative care nurse working out calculations for doses of morphine etc!
However, i reckon if you dont use it you lose it
Thanks for ya help :)

[tamborine]

£600 minus 17.5% = £495....VAT £105 - surely not?

[another-view]

You need a new calculator tambo.

[bednobs]

that's the trap i kept wanting to fall into Tam, but i knew the answer wasn't right!

[tamborine]

;) the keys do stick

[jake-the-peg]

The amount you have is the original amount + 17.5% of that so 600 divided by 117.5 is 1% of the original amount multiply by 100 gives you the original amount.

Algebraically if the amount you want is N

N*117.5/100 = 600

so 600 * 100/117.5 =N

[ChuckFickens]

Tambo, you don't work out 17.5% of 600. the VAT is 17.5% of £510.64

[another-view]

You can't just take 17.5% off!

Imagine you had £110 including 10%. You wouldn't say 10% of £110 is £11 so 110-11=£99

[tamborine]

Same figure from bank calculator.... ;)

[another-view]

lol daft lad :-)

[ChuckFickens]

That'll be because it's not the maths your getting wrong, it's the method.

[tamborine]

chuck I did say "minus"

[tamborine]

there's a calculator on Windows/Accessories

[redman41]

£495.00 plus 17.5% = £600.00

[ChuckFickens]

No it doesn't

495 + 17.5% = 581.63

[KARL]

tamborine, imagine your figure including VAT is £117.50 - you intuitively see that the original figure is £100 onto which was added VAT of £17.50......, no ? Well, if you take 17.5% (i.e. £20.56) from the £117.50 total you end up with not £100 but £96.94. This is where you went wrong - the 17.5% is calculated on the net figure, not the gross. The error is in the method (as alreadfy pointed out), not the calculator. To get from the gross to the net you divide by 1.175 because the gross figure is 1.175 tomes the net.