Date: 08/21/97 at 13:11:47 From: Anonymous Subject: Buying Stamps Dr. Math, I am an adult who is taking a correspondence course in Algebra I. I have the following question, and the textbook has not addressed this kind of problem. If you could please guide me through the steps of solving it, I would be very appreciative. A man purchases some .02 and some .15 cent stamps at the same time. He pays $1.56 for all the stamps. There are 10 more .02 stamps than .15 stamps. How many of each kind did he buy? Thanks, Sherell
Date: 08/22/97 at 15:04:27 From: Doctor Beth Subject: Re: Buying Stamps Okay, we'll have to decide to let a variable equal something, perhaps the number of .15 stamps. If x is the number of .15 stamps we buy, then the number of .02 stamps is 10 more, so it's x + 10. When the man purchases the stamps, he spends $1.56, but we also know that he spends .15x + .02(x+10), because the amount spent is the number of stamps times the price of each stamp. So now we have the equation 1.56 = .15x + .02(x+10) To solve for x, first I'll multiply and get 1.56 = .15x + .02x + .2 Now I'll combine .15x and .02x to get .17x, and subtract the .2 from both sides, to get 1.36 = .17x Dividing both sides by .17 gives us 8 = x So now we know that 8 = x, but we're not quite done - we have to make sure that we're answering the question in the problem. Since x was the number of .15 stamps, the man purchased 8 of the .15 stamps. The number of .02 stamps that he bought was x+10, so it must be 18. You can even check your answer by seeing that if you buy 8 stamps at 15 cents each, and then buy 18 stamps that each cost 2 cents, that you spend $1.56. Good luck in your course! -Doctor Beth, The Math Forum Check out our web site! http://mathforum.org/dr.math/
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