
Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion 
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October 22nd, 2014, 07:16 AM  #1 
Senior Member Joined: Nov 2010 From: Indonesia Posts: 2,001 Thanks: 132 Math Focus: Trigonometry  Multiplication or Division in Daily Life Problem Which Involves Negative Number
Can anyone give me some examples of daily life problems which involve negative numbers in multiplication and division? One for multiplication and one for division. Thank you very much.

October 22nd, 2014, 07:26 AM  #2 
Global Moderator Joined: Nov 2006 From: UTC 5 Posts: 16,046 Thanks: 938 Math Focus: Number theory, computational mathematics, combinatorics, FOM, symbolic logic, TCS, algorithms 
Dividing loan payments over a number of periods, perhaps?

October 22nd, 2014, 07:36 AM  #3 
Senior Member Joined: Apr 2014 From: Glasgow Posts: 2,156 Thanks: 731 Math Focus: Physics, mathematical modelling, numerical and computational solutions 
I don't think negative numbers are used much in daily life. The only examples I can think of are temperature scales, but they are rarely involved in multiplication and division calculations. Furthermore, most examples can be made positive by considering losses or bills rather than gains. One example could be related to depreciation in value of a car. i) Over the years 2000  2005, a car devalues in price from £3400 to £3250. What was the change in value? ii) Over the years 20052010 the car devalues again by 2.5 times the amount that it devalued in the preceding five years. What was the change in value in the car over the time period 2005  2010? You can make a similar division problem with this too. In fact a division problem might be more realistic since a car typically devalues more slowly over time. 
October 22nd, 2014, 09:47 AM  #4 
Senior Member Joined: Nov 2010 From: Indonesia Posts: 2,001 Thanks: 132 Math Focus: Trigonometry 
Uh, sorry, I forgot to mention that it was aimed for Middle Schoolers. Aren't those examples too complicated for them? Thanks for the inputs, though.

October 22nd, 2014, 10:13 AM  #5 
Senior Member Joined: Dec 2013 From: some subspace Posts: 212 Thanks: 72 Math Focus: real analysis, vector analysis, numerical analysis, discrete mathematics 
A thermometer and forecast use negative numbers 4  5 months per year. Also some settings on computer are given as negative numbers, like left_margin = 0,6. 
October 22nd, 2014, 10:25 AM  #6 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,671 Thanks: 2651 Math Focus: Mainly analysis and algebra 
Any measure that (sometimes) is negative could be averaged. That would give a division problem. Similarly, if the average of 4 measurements is 3, and the 5th measurement is 2. What is the new average? 
October 22nd, 2014, 02:56 PM  #7 
Senior Member Joined: Nov 2010 From: Indonesia Posts: 2,001 Thanks: 132 Math Focus: Trigonometry 
And what about the multiplication example?

October 22nd, 2014, 05:30 PM  #8 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,671 Thanks: 2651 Math Focus: Mainly analysis and algebra 
The second one of mine involves multiplication.

October 22nd, 2014, 05:31 PM  #9 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,671 Thanks: 2651 Math Focus: Mainly analysis and algebra  
October 23rd, 2014, 09:19 AM  #10 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,597 Thanks: 1038 
If you want (as example) to teach how to divide 1000 by 77, why do you want to create a useless "word problem story", as generally seems to be the case way too often as far as I'm concerned. 

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