Old Dominion Heather Posted November 18, 2008 Share Posted November 18, 2008 I'm sure I am just not thinking about these in the correct way so maybe you guys can help me out. We are stuck on these two from CWP 4: I do, of course, have the answers in the back, but I'm not seeing how they solved them. If you have the book, they are on pages 76 and 82, respectively. #1: A man filled his gas tank with 18.6 gal of gas. If 3 gal of gas cost $4 and he paid with two $20 dollar bills, how much change did he get? and #2: 4 books and 5 magazines cost $103.60 altogether. 8 books and 3 magazines cost $134.40 altogether. How much less does each magazine cost than each book? :lurk5: Thanks! Quote Link to comment Share on other sites More sharing options...
Old Dominion Heather Posted November 18, 2008 Author Share Posted November 18, 2008 Ok, I got #1. still looking for an answer to #2. Quote Link to comment Share on other sites More sharing options...
Deidre in GA Posted November 18, 2008 Share Posted November 18, 2008 i'll take a stab at the first one. if 3 gals cost $4, divide to find the cost of 1 gal. then, multiply the cost of one gallon times 18.6. it actually comes out to an even number. then subtract from $40 to find the correct change. this seems multi-step but simple - which always worried me with SM! maybe i'm missing something! (since you have the answer, i'm assuming you just wanted a process.) as for #2 - aaarrgh! i hated those kinds of problems! Quote Link to comment Share on other sites More sharing options...
nmoira Posted November 18, 2008 Share Posted November 18, 2008 (edited) #2: 4 books and 5 magazines cost $103.60 altogether. 8 books and 3 magazines cost $134.40 altogether. How much less does each magazine cost than each book?If 4 books and 5 magazines cost $103.60 then 8 books and 10 magazines cost $207.20 (draw the bars at this point). Since the difference between the two sets is now 7 magazines (10-3), then 7 magazines are $207.20-134.40= $72.80. Plug it back into one of the formulas: Each magazine is $10.40 and each book is $12.90. Edited November 18, 2008 by nmoira typo Quote Link to comment Share on other sites More sharing options...
jamnkats Posted November 18, 2008 Share Posted November 18, 2008 (edited) I did it differently. Adding everything together, you get 4b (books) + 5m (mags) +8b + 3m = $238 OR 12b + 8m =238 since 4b + 5m = 103.60 (from the word problem), then 4b=103.6 - 5m then 12b = 3 times 4b = 3 * (103.6 - 5m) = 310.8 - 15m substituting in the first equation, since 12b = 310.8 - 15m then, 310.8 - 15m + 8m = 238 and -7m = -72.80 so magazines = 10.40. From magazines we can get books from an earlier equation (4b=103.6-5m) and substitute 4b = 103.6 - (5 * 10.40) 4b = 103.6 - 52 4b = 51.60 books = 12.90 So, the answer (how much less does each mag cost vs each book) 12.90-10.40=2.50, so each magazine is cheaper by $2.50 than each book. Edited November 18, 2008 by jamnkats Quote Link to comment Share on other sites More sharing options...
nmoira Posted November 18, 2008 Share Posted November 18, 2008 I did it differently. Adding everything together, you get 4b (books) + 5m (mags) +8b + 3m = $238 OR12b + 8m =238 Cheater. :D You're not allowed to use algebra in CWP. :tongue_smilie: Quote Link to comment Share on other sites More sharing options...
jamnkats Posted November 18, 2008 Share Posted November 18, 2008 Cheater. :D You're not allowed to use algebra in CWP. :tongue_smilie: Oh! Sorry. I had no idea. I can't even begin to figure out how to do it without algebra though. Maybe *I* need to learn Sinagpore math. Quote Link to comment Share on other sites More sharing options...
nmoira Posted November 18, 2008 Share Posted November 18, 2008 Oh! Sorry. I had no idea. I can't even begin to figure out how to do it without algebra though. Maybe *I* need to learn Sinagpore math. :D Quote Link to comment Share on other sites More sharing options...
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