Calculating GST at 15% - Excel

They're not inherently more accurate than decimals at all. The problem is that people will "solve" a fraction first then round the resulting quotient and use that in the rest of the equation instead of looking at a fraction as 2 separate operators in an equation.

geek_ross1970, Oct 29, 11:43 pm


me? it just irritates me that two pathetic characters can argue about something so trivial that is pathetic........... so the word of the day is PATHETIC

geek_dino7, Oct 29, 11:44 pm


I agree, facepalms.

Does life exist elsewhere...

geek_johnf_456, Oct 29, 11:49 pm

Christ, even biker did better than you two.

That's pathetic!

geek_cybertao, Oct 29, 11:52 pm

There is no such thing as a stupid question. After all, this is a forum for asking such things. Every question is a simple question if you know the answer so no need to be a smart ar*e just because you think its stupid. I can also bet that the person who asked the question know lots of thing you righteous #%$ dont. Just answer the question or are you feeding off someone elses answer to make yourselves sound clever when you didnt know it yourself. Racheal77, sorry there are so many as#$holes out there.

geek_eurika, Oct 30, 8:20 am

My answer is at post #16.Where's yours?Or are you just being a self-righteous #%$?

geek_cybertao, Oct 30, 8:23 am

AB
1)
2)10015% =A2*(1-B2) 85100 les 15%
=A2*(1+B2) 115100add15%
=A2*(1+35%) 135
=A2*15% 1515% of 100

and back in the day(gross X15)/100

And yes IRD will allow you to use true percentage as long as the same calculation is used for GST on Sales / income as is used on Purchase/ Expense

remembering 12.5% of 100 =12.5not 100/9=11.111111111

geek_prickles1, Oct 30, 10:23 am

112.5 / 9 = 12.5
Just like how 115 / 23 * 3 = 15

geek_cybertao, Oct 30, 10:55 am

How is it trivial? Mathematics is very important and useful unless you wish to only ever be a shelf restocker at The Warehouse.

geek_biker_69, Oct 30, 12:30 pm

Still waiting on you to show the rest of those workings, cybertoss. You know, all the extra convoluted steps.

geek_biker_69, Oct 30, 12:31 pm

Well that's what I worked out as well.Seems a heck of a lot easier than any of the other formula's out there.

geek_jimminette, Oct 30, 12:46 pm

You want to learn how to find a fraction that represents a decimal?Google it already.

Otherwise the work done with the fractions is same each time, and I'll go through it using current GST.
GST costs 3/20ths of the original price, 3 / 20 = 0.15 (or 15% - 115/100).
So you break the original price into 20ths, GST is three of those.Original Price / 20 * 3 = GST.In practice it is best to save the divisor for last and use Original Price * 3 / 20 = GST
If you don't care what the GST is but want Original Price + GST, that is 20/20ths (Original Price) + 3/20ths (GST) = 23/20ths.So Original Price / 20 * 23 = Original Price + GST.Better calculated as Original Price * 23 / 20.

If you want to find the GST content or original price, start by treating it as 23/20ths.
GSTinc Price * 20 / 23 = Original Price
GSTinc Price * 3 / 23 = GST

geek_cybertao, Oct 30, 1:01 pm

It was simpler when GST was 12.5% because 12.5% = 1/8th

Original Price *1 / 8 = GST, is the same as Original Price / 8 = GST

8/8ths (Original Price) + 1/8th (GST) = 9/8ths
Original Price * 9 / 8= Original Price + GST

GSTinc Price * 8 / 9 = Original Price
GSTinc Price * 1 / 9 = GST, or GSTinc Price / 9 = GST

geek_cybertao, Oct 30, 1:07 pm

Cybertao - some people can't "see" fractions, so they prefer to use something like "x 1.15" or "x 0.15/1.15" because they can't "see"that 1.15=23/20=115/100 and 0.15/1.15=3/23 or that 0.15=3/20=15/20.

geek_4pc, Oct 30, 1:10 pm

Crikey this nonsense is still going!

geek_johnf_456, Oct 30, 1:20 pm

geek_umegaoka, Oct 30, 1:25 pm

No need. I already have full understanding of the process.

You called the method I demonstrated 'convoluted' when in fact it is much faster, simpler and less convoluted and no less accurate.

geek_biker_69, Oct 30, 1:47 pm

You clearly don't understand.

geek_cybertao, Oct 30, 1:48 pm

Using the method I outlined it's no more or less difficult regardless of what the GST rate is. Or any other percentage you need to calculate for that matter.

geek_biker_69, Oct 30, 1:50 pm

Yeah, so why not do it the proper and accurate way?

geek_cybertao, Oct 30, 1:51 pm

I fully understand - it's intermediate school maths to convert a decimal to a fraction. However, the fact you won't show the convoluted workings to find the fraction equivalent just proves you're wrong about your assertion.

geek_biker_69, Oct 30, 1:52 pm

Grabs the popcorn, going to be a long night..

geek_johnf_456, Oct 30, 1:53 pm

It's no less accurate to use decimals - the figure was 15.23568%. Not 95223/625000%.

geek_biker_69, Oct 30, 1:54 pm

Nah, I'm going fishing shortly. Although I may be back later to further play this hooked moron!

geek_biker_69, Oct 30, 1:55 pm

Playing with yourself is something you should keep private.

geek_cybertao, Oct 30, 2:00 pm

It's good that your mummy explained that to you.

geek_biker_69, Oct 30, 2:03 pm

wow.. one person asks how to calc. gst and 3 pages later, the sky is still falling.. hehehehe, thanks for the entertainment

geek_joanne01, Oct 30, 2:18 pm

Bump, you back yet biker from fishing

geek_johnf_456, Oct 30, 9:07 pm

Not then. But I am now!

'cybertoss' has run away to look liek a fool another day.

geek_biker_69, Oct 30, 11:38 pm

What's the equation to divide Stephen Donald into 23 parts please?

geek_ross1970, Oct 30, 11:49 pm

Stephen Donald?

geek_biker_69, Oct 31, 11:59 am

Hi biker, good to see you again.What's one third in percentage form?

geek_cybertao, Oct 31, 12:12 pm

Go into "sports" keyword search "donald" last 24hrs ...... all will become obvious.

geek_ross1970, Oct 31, 12:13 pm

If you want to be accurate to two decimal places, do your calculating to three decimal places.

geek_rahto, Oct 31, 3:39 pm

See post #99. Then post your workings used to get the fractions you did to do exactly the same thing as using the method with the simple formulas I posted at #45, #70 & #74. Then we'll see who is convoluted.

geek_biker_69, Oct 31, 4:15 pm

geek_mark.p, Oct 31, 4:22 pm

Just answer the question, biker.You don't even need to show me your working.

geek_cybertao, Oct 31, 4:23 pm

This all reminds me of a question that was asked in a high school exam.

"With the use of a standard barometer, describe how to find the height of a high rise building".

One obviously bored student answered:
There are 4 ready ways to find this:

1. Measure the air pressure at ground level, then travel to the top of the building, measure the air pressure again and then, using a suitable formula with the differential pressure, calculate the height.

2. Travel to the top of the building, tie a long piece of inextensible string on to the barometer, lower it over the side until it touches the ground, pull it up and measure the length of the string!

3. Throw the barometer from the top of the building, timing the fall with a stopwatch until it hits the ground. Use the elapsed time in the appropriate 'law of motion' formula to calculate the height.

4: Go to the caretaker of the building and say, "If you tell me the height of your building, I'll give you this nice barometer"!

There are many ways to skin a cat, some are easier, some are more obvious, some are more memorable etc.

When it comes to calculating GST, of course it can be accurately and comprehensively done, on the fly, using a suitable layout with suitable fomulae on a spreadsheet.

But sometimes, someone just wants an easy 'rule of thumb' way to calculate with or without a calculator.

geek_tmenz, Oct 31, 4:25 pm

I recall this I think. They threw the barometer off and worked out by timing it and then had to fight to get the method accepted or something. lol

geek_jcmp21, Oct 31, 4:28 pm

The easiest way to manipulate numbers without the use of a calculator is to use fractions.

Even if you choose to use decimals, there is no excuse for ignorance and not knowing a fundamental basic of maths - especially when all the other methods are derivatives.

geek_cybertao, Oct 31, 4:36 pm

agree fully

unfortunately although the education system in this country keeps patting itself on the back I reckon they're doin a very poor job these last 30 years or so with teaching the BASICS of maths and english.......

chooks are roosting about now.....

geek_drcspy, Oct 31, 4:37 pm

Bumping the mathlete battle thread

geek_jcmp21, Oct 31, 5:00 pm

What's your recent involvement? My 5yo nephew has a basic grasp of fractions and he's 5. I'd say the syllabus has advanced since I was at school..... what's gone backwards is parenting, but they try to blame the schools.

Oh god this now belongs in general.....

geek_smac, Oct 31, 5:12 pm

well I failed to mention that I do understand that things have started to swing back to basics..............because of the pisspoor results they were getting over the last two decades.......

geek_drcspy, Oct 31, 5:15 pm

Yes because the education system was being built around girls, pacific Islanders and Maori achieving.

geek_jcmp21, Oct 31, 5:36 pm

Not until you show your convoluted workings to turn the decimals into fractions, so you look an even bigger fool.

geek_biker_69, Oct 31, 5:48 pm

To add GST to the price in cell A1. =SUM(A1*(15%+1))

geek_lythande1, Oct 31, 5:49 pm

Rubbish. It's easier to divide by 1.1523568 than it is to divide by 720223/625000 especially considering the need to first convert the decimal to an equivalent fraction and given that there's no increased accuracy whatsoever.

We were taught long division -I guess they skipped it for you 'mixed abilities' crowd.

geek_biker_69, Oct 31, 5:56 pm

1) Please express 1/7 accurately as a decimal.

2) Please show me any decimal number that can't trivially be expressed just as accurately as a fraction.

geek_little_egypt, Oct 31, 6:10 pm

You multiply by 625000 and divide by 720223.

geek_cybertao, Oct 31, 6:12 pm