Adding Fractions That Have VariablesDate: 03/24/2002 at 13:39:33 From: Sal Anicito Subject: Adding fractions with variables 9a 2 ---- + ---- 10 5 I have the answer in the back of the book but I don't know how to solve it. The answer is showing: 9a + 4 -------- 10 Date: 03/24/2002 at 13:45:11 From: Doctor Ian Subject: Re: Adding fractions with variables Hi Sal, Let's back up a step. Would you be able to handle this without the variable? That is, how would you add 9 2 -- + - = ? 10 5 Don't just tell me the answer. Show me the steps that you would follow. - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ Date: 03/24/2002 at 23:18:26 From: Sal Anicito Subject: Adding fractions with variables I would first find the LCD, which would be 10. Then say 5 into 10 is 2 and 2 x 2 = 4, which would give me 4/10. Then 10 into 10 is 1 and 1 x 9 is 9, which would give me 9/10. Then add 9 + 4, which is 13, so I would get 13/10 for an answer. Is that right? Date: 03/25/2002 at 07:09:14 From: Doctor Ian Subject: Re: Adding fractions with variables Hi Sal, That's exactly right. 9 2 9 2 2 9 4 13 -- + - = -- + - * - = -- + -- = -- 10 5 10 5 2 10 10 10 The thing is, it works the same way even if you have a variable in there: 9a 2 9a 2 2 9a 4 9a + 4 --- + - = --- + - * - = --- + -- = ------ 10 5 10 5 2 10 10 10 The only difference is that you don't know what the value of a happens to be. To see why this works, choose a value for a, but don't do the multiplication yet: 9*2 2 9*2 2 2 9*2 4 9*2 + 4 ----- + - = ----- + - * - = ----- + -- = -------- 10 5 10 5 2 10 10 10 A variable is just a number whose value you don't yet know; and a variable expression (like '9a') is just an operation that you're putting off until later. Does this help? - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ |
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