tmkclscroggins Posted April 8, 2008 Share Posted April 8, 2008 :confused:We are on Foerster's Algebra I, lesson 7-10, #9 A gas station has just raised its prices. The attendant resets the pump but forgets to record the old prices. Rather than revealing her forgetfulness, she consults yesterday's sales report. She finds that 450 liters of regular and 320 liters of unleaded were sold for a total of $384.83. Regular was 5 cents per liter cheaper than unleaded. What were the two prices per liter yesterday? We are solving problems using two variables. This is what I have so far: x = regular y = unleaded 450 x + 320 y = 384.83 What do you do about the 5 cents cheaper? ( y - 5???) Can you walk me step by step throug this? Thanks, Melissa Quote Link to comment Share on other sites More sharing options...
Maverick Posted April 8, 2008 Share Posted April 8, 2008 Since regular is 5 cents cheaper than unleaded, x = y-5, or you can say y = x+5. Plugging that into your original equation: 450x + 320(x+5) = 384.83 Quote Link to comment Share on other sites More sharing options...
tmkclscroggins Posted April 8, 2008 Author Share Posted April 8, 2008 Thanks, Maverick....that makes sense! m Quote Link to comment Share on other sites More sharing options...
Sharon in MD Posted April 8, 2008 Share Posted April 8, 2008 :confused:We are on Foerster's Algebra I, lesson 7-10, #9 A gas station has just raised its prices. The attendant resets the pump but forgets to record the old prices. Rather than revealing her forgetfulness, she consults yesterday's sales report. She finds that 450 liters of regular and 320 liters of unleaded were sold for a total of $384.83. Regular was 5 cents per liter cheaper than unleaded. What were the two prices per liter yesterday? We are solving problems using two variables. This is what I have so far: x = regular y = unleaded 450 x + 320 y = 384.83 What do you do about the 5 cents cheaper? ( y - 5???) Can you walk me step by step throug this? First you are right with the initial basic idea....take 450X +320Y = 384.83 but then notice that the cost of regular, X, is .05 less than the price of Y, so substitute Y-.05 for X thus: 450X + 320Y = 384.83 becomes 450(Y-.05) +320Y = 384.83 then multiply through by 450 450Y - 22.50 + 320Y = 384.83 then add the 22.50 to the other side... 450Y + 320Y = 407.33 combine like terms 770Y = 407.33 then divide by 770 Y=.529 cents this is the price of unleaded. subtract .529 - .05 = .479 cents for regular Check 450 X .479 = 215.55 regular sold 320 X .529 = 169.28 unleaded sold 215.55 + 169.28 = 384.83 total sales. HTH Quote Link to comment Share on other sites More sharing options...
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