without all the "should we or shouldn't we" have a 15% gst my question is...what is the backwards calculation for a 15% gst? eg 10% gst $100 +10% = $110 backwards...$110 -(110/11) = $100 I thought the logical was 12.5%gst because it's reverse was divide x 9 $100 +12.5% = $112.5 backwards...$112.5 -(112.5/9) = $100 so....100 +15% = $115 backwards....$115-(115/ x ) = 100 I come up with 7.66666666666 ????? surely it will not be that cumbersome?? aggghhh my bookeeping OCD will HATE this if my books are out by a few cents

Our friends in the UK have already had multiple VAT increases http://www.startinbusiness.co.uk/flowchart/8flowchart_vat_deduct.htm Leverage off their work

In NZ we take GST figure divide by 23 and multiply by 20 eg 115/ 23 x 20 = 100. Bit more convoluted than 10% but it works.

Oops sorry, I replied to this last night and lost the post Thanks for those answers, I was getting so hung up on the "divide by" number I could not see the other answers.

I've seen people do these calculations, but it's never made sense to me. Why don't you just divide by (1+GST)?

Yes that is the link D.T posted If we assume that VAT is at a rate of 15%... Gross price divided by 1.15 = Net price Price after tax divided by 1.15 = Price before tax or in fractional form (which is Charlottes answer) Price after tax divided by 23/20 = Price before tax.

But is it really easier to type "*23/20" instead of "/1.15"? Feels like American betting odds to me...

Whole numbers for the dummies. One pollie this morning said there'd be more $ for xy&z. I laughed at his lack of understanding of the gst, it is a State tax collected by the Fed's and returned to the states. If anything, it will allow the feral gummint to redistribute its own budget allocations.

Hope it doesn't go through, I remember most things went up by more than 10% when they 1st brought in the GST.

A GST increase will only create more full-on bogans. At the moment there are people tinkering on the bogan threshhold. A sudden increase in their cost of living and whammo, they turn into a bogan. I've seen it happen.

Currently with GST at 10% you divide the full cost by 1.10 to get the base cost. If GST becomes 15% you'd divide the full cost by 1.15 to get the base cost. If GST becomes 22% you'd divide the full cost by 1.22 to get the base cost. The equation is: Base cost x (100% + GST%) = Full cost - or - Base cost = Full cost / (100% + GST%) Roughly year 8 level algebra.

the calculation to find the GST component just becomes a two part equation with 15% where as now it just a "divide by 11 for get the gst component" Gst component will be gst = gross cost - (gross/1.15) no biggie, just getting my head straight.

The problem is people have been taught to think in fractions rather than percentages. It's a throwback to when we used pounds and shillings as our currency and feet and miles as distance. You can think, "divide by 11 and multiply by 10", but that only works when the numbers are convenient. It become a complete mess if the GST component become 11.624%. If you think in percentages then the conversion is simply multiplying or dividing by 1.11624. The solution is very simple, but 3 generations on and our schools and even our language is still imparting a completely redundant and very inaccurate way of doing mathematics. Some kids figure this out in early high school and go on to become engineers, scientists, physicists, etc. Those who don't have that light bulb moment in year 8 tend to drop maths at the first opportunity.

If you're doing these calculations in a spreadsheet, don't forget to round the result each time. Otherwise totalling a number of calculated fields may not appear to give the excat result.

I was a bit distressed to learn that my son (year 1) is being told "getting the correct answer isn't as important as understanding the process" in maths. To which I respond - if you aren't getting the correct answer, you don't understand the process! This isn't social studies - there is ALWAYS a correct answer in maths (see note 1) (Note 1 - rounding errors notwithstanding - also see note 2) (Note 2 - there is also room for interpretation in the conventions of order of operations which may lead to differences in what is understood to be the correct answer - also see note 3) (Note 3 - don't get me started on non-algebraic maths - also see note 4) (Note 4 - complex numbers? unrepresentable values? etc etc?)

I'm yet to see a year 1 that gets all questions right every time, even if they understand the process. I would wholeheartedly agree with the statement that the process is more important. If you know that 3+4=7 then that's great, but the solution of 4+3 might still be a complete mystery to you if you don't understand the process.

The process is the important part not the answer. Granted if you get 100% of the process correct you get the correct answer, but if you get 99% of the process correct and 1% wrong you get the wrong answer. Trust me if you failed a question based on the answer the majority of people would fail all Maths based tests. Conversely you can get every answer wrong in an exam and still get a high distinction!