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Quadratic Equation Problem
By Jenny Peters on Friday, November 09, 2001 - 06:59 pm:

I've got this question which I am supposed to form a quadratic equation from but I haven't got a clue how to get a quadratic equation out of it -

"When the average speed of a car increases by 10km/h the time it takes to travel 105km reduces by 15 mins. Find the average speed of the car before the increase."

If anyone could help me out and explain how to go about getting a quadratic equation out of it I'd be very grateful. Sorry if this is posted in the wrong place I wasn't sure where to put it.

By Arun Iyer on Friday, November 09, 2001 - 07:34 pm:

Well Jenny,
we know that......
average speed = total distance/total time

let velocity before the increase be v and time taken be t. Hence,
v=105/t......(1)

After the increase, we get,
(v+10)=105/(t-15).......(2)

equation (1) - equation(2) gives,
10 = [105/(t-15)]-[105/t]

On simplifying this you will get a quadratic equation in variable t....

Hope this is clear......

love arun