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 March 3rd, 2012, 10:29 PM #1 Newbie   Joined: Mar 2012 Posts: 6 Thanks: 0 I am a little Confused. Hello, I have a problem that I don't know how to solve. Could someone please explain to me what I am suppose to do? "A car leaves a town traveling at 40 miles per hour. Two hours later a second car leaves the town traveling the same route and overtakes the first car in 5 hours and 20 minutes. How fast was the second car traveling?" March 3rd, 2012, 10:43 PM #2 Senior Member   Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 522 Math Focus: Calculus/ODEs Re: I am a little Confused. Both cars travel the same distance, while the first car travels for 2 hr more. Let t be the time for the second car then t + 2 is the time for the first car. Let v be the speed of the second car which we assume is constant. Using distance equals rate times time, we may state: We are told giving us: March 4th, 2012, 07:47 AM #3 Global Moderator   Joined: Dec 2006 Posts: 21,113 Thanks: 2327 The second car made up 80 miles in hours, so its relative velocity was 15 mph. Hence the answer is 55 mph. March 8th, 2012, 03:39 PM   #4
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 Originally Posted by MarkFL Both cars travel the same distance, while the first car travels for 2 hr more. Let t be the time for the second car then t + 2 is the time for the first car. Let v be the speed of the second car which we assume is constant. Using distance equals rate times time, we may state: We are told giving us:
Could you explain to me how you got that answer? March 8th, 2012, 04:17 PM #5 Senior Member   Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 522 Math Focus: Calculus/ODEs Re: I am a little Confused. We begin with distance equals rate times time. We let v be the rate of the second car, since we don't know the rate and this is what we're asked to find. If the second car traveled for 5 1/3 hr and the first car left 2 hours before the second then the second car traveled for 7 1/3 hr at 40 mph. Since they both traveled the same distance d we may state: Now we solve for v: March 9th, 2012, 06:52 PM #6 Newbie   Joined: Mar 2012 Posts: 6 Thanks: 0 Re: I am a little Confused. Thanks for the explanation. I have another one as well. How much water needs to be removed from 20 gallons of 30% salt solution to change it to a 40% salt solution? March 9th, 2012, 07:20 PM #7 Senior Member   Joined: Jan 2012 Posts: 131 Thanks: 0 Re: I am a little Confused. 30%(Salt) of 20 gallons of solution= 6 gallons 40%(Salt) of x gallons solution= 6 gallons x=15 gallons. H20 to be removed=5 gallons. March 9th, 2012, 07:24 PM #8 Senior Member   Joined: Jul 2010 From: St. Augustine, FL., U.S.A.'s oldest city Posts: 12,211 Thanks: 522 Math Focus: Calculus/ODEs Re: I am a little Confused. I would state 30% of 20 gallons is 40% of how many (x) gallons? Writing this mathematically where 20 and x are in gallons: Since 20 - 15 = 5, we see 5 gallons of water must be removed. March 10th, 2012, 01:26 PM #9 Newbie   Joined: Mar 2012 Posts: 6 Thanks: 0 Re: I am a little Confused. Okay, I have another one. "Suppose that the perimeter of a square equals the perimeter of a rectangle. The width of the rectangle is 9 inches less than twice the side of the square, and the length of the rectangle is 3 inches less then twice the side of the square. Find the dimensions of the square and the rectangle." March 10th, 2012, 02:29 PM #10 Global Moderator   Joined: Oct 2008 From: London, Ontario, Canada - The Forest City Posts: 7,976 Thanks: 1158 Math Focus: Elementary mathematics and beyond Re: I am a little Confused. Hi, Siedas. In future please start a new topic for a different (unrelated) question. Let W be the width of the rectangle. Let L be the length of the rectangle. Let s be the side of the square. From the given information W = 2s - 9 and L = 2s - 3. Since perimeter equals 2 times length plus two times width we have 2W + 2L = 4s 2(2s - 9) + 2(2s - 3) = 4s 4s - 18 + 4s - 6 = 4s 4s - 24 = 0 4s = 24 s = 6, so the side of the square is 6, the width of the rectangle is 2(6) - 9 = 3 and the length of the rectangle is 2(6) - 3 = 9. Tags confused Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post charlieboon Calculus 5 February 23rd, 2013 11:01 AM ccfoose Algebra 3 April 16th, 2012 10:55 PM katfisher1208 Algebra 1 April 20th, 2010 07:59 PM momoftwo New Users 4 August 19th, 2009 07:15 PM charlieboon Algebra 0 December 31st, 1969 04:00 PM

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