Teacher2Teacher |
Q&A #19693 |
From: Gail
(for Teacher2Teacher Service)
Date: Jul 25, 2008 at 08:08:04
Subject: Re: Applications of Percents
Hi Andrea, Have you tried giving them a proportional picture of the problems? Something like this: 0_________________________1/2 of total_______________________total 0% 50% 100% Each problem we solve in my classroom, we use this same model. Students begin by filling in the data they know from the problem, and placing a letter (unknown) at the spot where they are looking for a solution. For example, if the problem is "what percent of 60 is 12?" we would draw this: 0_________12________________30_______________________60 0% n 50% 100% Now we can use proportional reasoning to solve the problem, or we can just set up a proportion and cross multiply to solve it... 12/n = 60/100 12 x 5 = 60 n x 5 = 100 n = 20 If the problem were "40% of 56 is what number?" we would set it up this was: 0___________________n______28_______________________56 0% 40% 50% 100% My students know how to determine 10% and 1% quickly, and would use those skills to say that 10% of 56 is 5.6, so 40% of 56 is 4 times as great, or 22.4 The purpose of the visual is to check for reasonableness, and to give students a framework for solving any percent problem that comes along. They have this one method that will work each time. I hope this gives you something to start with. :-) Gail -Gail, for the T2T service
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