Karen in CO Posted September 22, 2010 Share Posted September 22, 2010 We had rounding decimals in math today which is easy, BUT my dd9 wanted examples of why you would want to do it. Please help me find some useful examples of why you would want to round a decimal from the hundreths to tenths or thounsandths to hundredths. I could think of anything that a 9yo could relate to. She always thinks more precise is better. Thanks. Quote Link to comment Share on other sites More sharing options...
Dmmetler Posted September 22, 2010 Share Posted September 22, 2010 The best example I've seen is gas pumps, which still sometimes list prices in fractions of a cent-but you can't pay a fraction of a cent, so the final price rounds to the nearest hundredth. Also, the stock page of the newspaper, where stock shares are listed in very small quantities, and, again, you'd round in actual purchasing. Both those use fractional notation, not decimal, though. Quote Link to comment Share on other sites More sharing options...
silver Posted September 22, 2010 Share Posted September 22, 2010 Sales tax is a good example. It's calculated by percentage, which results in fractions of a cent. That has to be rounded so that we can pay. The main reason for rounding is when you're dealing with measurements. A lot of times you might round because you don't have the precision that you'd be claiming if you didn't round. An example of this is calorie counts on food. In the US, calorie counts are always rounded. If the manufacturer has a bunch of granola bars tested and the average calorie count is 92.3, they're going to print "90 calories" on the packaging. It would be misleading to print "92.3 calories" because every single bar they produce doesn't have exactly 92.3 calories. The machines that measure out ingredients and cut the bars to size are precise--but they're not that precise. Quote Link to comment Share on other sites More sharing options...
kiana Posted September 22, 2010 Share Posted September 22, 2010 Sales tax, percent off sales in stores, measurement, etc. Telling people that you're 4 ft 10.49230525232 inches just sounds silly, but 4 ft 10 and a half sounds reasonable. If something that costs 9.95 is 25% off, does that mean they expect you to pay $7.4625 ? No, they expect you to pay $7.46, but then they'll put tax on that, which is unlikely to be a whole number ... Quote Link to comment Share on other sites More sharing options...
truebluexf Posted September 22, 2010 Share Posted September 22, 2010 It's also helpful when shopping. $7.99 tricks your mind into thinking something is $7, when it's really more like $8. Quote Link to comment Share on other sites More sharing options...
Rosie_0801 Posted September 22, 2010 Share Posted September 22, 2010 We use rounding whenever we use money, nearly, because we don't have one and two cent coins anymore. Rosie Quote Link to comment Share on other sites More sharing options...
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