The problem is that the manufacturers in the US are not ‘thinking metric’. If the cereal package was a logical metric size (say 500 g), then the issue starts to look much easier. The unit price then would (most likely) be in $/kg – in your example $7.72/kg. And that actually is an interesting price point. Here in the UK, where unit pricing is usually in £/kg (occasionally £/100 g, but easy to move the decimal point one place to convert to £/kg), £7/kg (or £0.70/100 g) is a common pricing level. Cheese, fresh fish, many meats etc. often come in somewhere in the region of £7/kg. I find it a very useful comparator in assessing whether something is good value or not (obviously depends on the product – imported gourmet cheese is often priced at around the £10 to £12/kg level).
So a package weighing, say, 250 g, and costing say £1.48, can be easily worked out at 4 x 1.48 – say 4 x 1.50 for ease of calculation = £6/kg. That is under my £7/kg pricing comparator level, so probably a good buy (again, depending on the product). Multiplying is always easier than dividing, and for anything weighing less than 1 kg, you can usually use multiplication rather than division to work out its unit price per kg. Having to use oddball sizes like 368 g (compared to 13 ounces) is always difficult. If say the weight was 375 g (still a bit of an oddball size, but at least exactly halfway between 250 g and 500 g), that would then be an odd size in ounces, which surely makes calculating non-metric unit prices (where not given) much more difficult. John F-L From: Paul Rittman Sent: Sunday, February 12, 2012 5:22 AM To: U.S. Metric Association Subject: [USMA:51457] Calculating prices with grams and ounces The last few times I went shopping for breakfast cereal, I tried to compare the prices of various cereals on a per-ounce or –gram basis. Tonight, one cereal I bought was $2.84, and the package said it weighed 13 ounces or 368 grams. Calculating the price per ounce seems to be much easier than calculating the per gram price. I was able to quickly see that it costs about 20 cents an ounce (quite a bit cheaper than most other cereals) by multiplying 13 x 2, and then adding a zero. I then decided to try to get the cost per gram, but decided not to even try to put 368 into 284. After a similar experience shopping last week, I saw that 20 cents an ounce was roughly equal to 0.7 cents a gram. I’m not sure that I want to multiply the number of grams by 7, and then move the decimal. Another option I thought of was to take a tenth of the gram total, and then subtract it 3 times (from that total), to see if the price was at 0.7 cents a gram or lower. Still, it seemed like a lot more work. I know folks can say it’s just that I’ve just gotten used to imperial measurements, but it does seem a lot easier to me to use when shopping, that’s for sure. Now I know that if our country were officially metric only, the supermarkets would be posting the prices in metric terms on the labels on the shelves, but honestly I don’t like to use them because the writing is so small (even when they are given with imperial units). OK now—is this simply a math process that I’ve forgotten about, that will allow me to calculate as easily with grams? Or is this simply an area where working with imperial units is easier? I am well aware of the various advantages of the metric system…. is this just an example of no system being perfect? No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.1913 / Virus Database: 2112/4803 - Release Date: 02/11/12
