SOLUTION: the distance between London and New York is 320 Km. A train takes x hours to travel between London and New York. (a) Write down an expression in terms of x, for the average speed

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: the distance between London and New York is 320 Km. A train takes x hours to travel between London and New York. (a) Write down an expression in terms of x, for the average speed       Log On


   

Question 1179148: the distance between London and New York is 320 Km. A train takes x hours to travel between London and New York.
(a) Write down an expression in terms of x, for the average speed of the train [1]
(b) A car takes 2 ½ hours longer than a train to travel between London and New York. The average speed of the train is 80 Km/h greater than the average speed of the car. Form an equation in x and show that it simplifies to

Found 2 solutions by josgarithmetic, mananth:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
A train takes x hours to travel between London and New York.

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Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
the distance between London and New York is 320 Km. A train takes x hours to travel between London and New York.
(a) Write down an expression in terms of x, for the average speed of the train [1]
Average speed of train = 320%2Fx%29 km/h
(b) A car takes 2 ½ hours longer than a train to travel between London and New York.
Let average speed of car be x Km/h
speed of train =x+80 Km/h
320/x - 320/(x+80) =5/2
(320(x+80) -320x)/(x(x+80))=5/2

320(x+80) -320x = x(x+80)*(5/2)
320x +25600 -320x =(x^2+80x)*(5/2)
25600=(x^2+80x) *(5/2)
51200=5x^2+400x
5x^2+400x -256000=0
x^2+ 80x -51200=0