Tips on Quickly Converting Fractions to PercentsDate: 02/14/2005 at 08:14:56 From: steve Subject: Dividing a number by a larger number I'm reviewing for a recruitment test. A majority of the math questions are percentages, eg. 9 as a percentage of 60. I know the formula as (9/60) * 100, but I don't know how to calculate 9/60 without using a calculator. Date: 02/14/2005 at 10:52:47 From: Doctor Ian Subject: Re: Dividing a number by a larger number Hi Steve, In the most general case, you just use long division. The fraction 9/60 just means '9 divided by 60', so 0.1 5 _______ 60 ) 9.0 0 --> 9/60 = 0.15 6 0 --- 3 0 0 3 0 0 ----- 0 You can simplify your life a little by trying to reduce the fraction, e.g., 9 3 * 3 3 -- = ------ = -- 60 3 * 20 20 In this case, you get a denominator that is a divisor of 100, which means you're golden: 3 5 15 -- * - = --- 20 5 100 which, of course, means the same thing as 0.15. (If you're not sure why, let me know, because this is a fairly important thing to understand.) If you just need to get an approximate answer, there are other things you can try. For example, 60 is a little more than half of 100. And 9 is half of 18, so it's a little more than half of, say, 15 or 16. So 9 15 or 16 -- = about -------- 60 100 On a multiple choice test, that might get you close enough to be able to pick out the actual answer. Note that it can be helpful to do the multiplication first, since in made-up problems, you can often get rid of the denominator by reducing it: 9 900 90 30 -- * 100 = --- = -- = -- = 15 60 60 6 2 Does this help? - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ Date: 02/14/2005 at 11:29:44 From: steve Subject: Thank you (Dividing a number by a larger number) Thank you very much for your reply. The information you provided me with was a great help. I've run through a few test questions, and I am now comfortably able to answer them using the methods you have suggested. Thanks again. |
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