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Stumped yet agian !! :(? If one-half of one integer is subtracted from three-fifths of the next consecutive integer, the difference is 3. What are the two integers? I would guess that I would set up this equation as 1/2 - 3/5 = 3 But I am lost after that , and I am not even sure thats how I should set it up. Help ! Also I need help with this problem. It is the well know "a train taveling a such and such speed equation" THANK YOU A passenger train can travel 325 miles in the same time a freight train takes to travel 200 miles. If the speed of the passenger train is 25 mi/hr faster than the speed of the freight train, find the speed of each. First one: 1/2 of an integer: 1/2x is subtracted from 3/5 of the next consecutive integer (which is x + 1): 3/5(x + 1) - 1/2x And the difference is 3: 3/5x + 3/5 - 1/2x = 3 Multiply through by 10 to make it easier: 10(3/5)x + 10(3/5) - 10(1/2)x = 10(3) 6x + 6 - 5x = 30 x = 24 So the integers are 24 and 25. Check: 3/5(25) - 1/2(24) = 15 - 12 = 3 check! Next one: distance (d) = rate (r) times time (t), so time (t) = distance (d) over rate (r), or t = d/r The problem tells us two things: 1) The passenger train travels 325 miles (at a rate of p miles per hour) : t = 325/p in the same amount of time that the freight train travels 200 miles (at a rate of r miles per hour): t = 200/r Since both times are equal, you can set the equations equal too: 325/p = 200/r Cross-multiplying: 325r = 200p And dividing both sides by 25 to make it look nicer: 13r = 8p 2) The speed of the passenger train (p) is 25 miles per hour faster than the speed of the freight train (r): r + 25 = p So now you have your 2 equations: r + 25 = p 13r = 8p Substitute in for p in the second equation using the first equation: 13r = 8(r + 25) = 8r + 200 5r = 200 r = 40 Then plug that back into the equation for p: p = r + 25 = 40 + 25 = 65 So the passenger train goes 65 miles per hour and the freight train goes 40 miles per hour. Check: The passenger train would travel 325 miles in 325 miles/65 miles per hour = 5 hours. The freight train would travel 200 miles in 200 miles/40 miles per hour = 5 hours. It works! (1) 3/5*(i+1)-i/2=3 => i=24 _______________ 325/Vp=200/Vf Vp=Vf+25 => Vf=40, Vp=65 1. 3/5(x+1)-1/2x=3 3/5x-1/2x=3-3/5 1/10x=12/5 x=24 the integers are 24 & 25 2. a=ime the trains run, bmiles/hour a x b = 200 a x (b+25) =325 200/a = (325/a) - 25 a=5, b=40 passenger train -- 65 miles/h, freight -- 40 miles/h 1. 3/5(x+1)-1/2x=3 3/5x-1/2x=3-3/5 1/10x=12/5 x=24 the integers are 24 & 25 2. a=ime the trains run, bmiles/hour a x b = 200 a x (b+25) =325 200/a = (325/a) - 25 a=5, b=40 passenger train -- 65 miles/h, freight -- 40 miles/h Ok, your first question Let's X = the first integer Based on your information, let X+1= second integer 3/5(X+1) - 1/2X=3 Multiply everything by 10 since least common denominator 6(x+1 - 5X= 30 6X+6 -5X= 30 X+6=30 X= 24 So X+1=25 So our integers are 24, and 25 Now Distance=Rate * time Let the time both trains take is Y Let X= speed of the freight train Let X+25= speed of passenger train freight train: 200= x*y passenger train 325= (x+25) y Solve for Y on both equation 200/x=y 325/(X+25)=y Now since they both equal y, set them equal 200/x=325/(x+25) cross multiply 200(x+25)=325x 200x + 5000 = 325x 5000= 125x 40 = x 65 = x+25 So speed of freight train is 40 mph and passenger train is 65 mph |
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