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## Homework Statement

A car moving at constant speed of 40 km/h in a straight road which heads towards a wall makes a 90

^{0}(90 degree) turn by the side of the wall. A fly flying at constant speed 100km/h starts from wall till car and when it reaches the car turns back and flies towards wall at same speed (100 km/h). This procedure starts when the car is 20 km away from the wall. The fly continues its journey till the car takes the 90 - degree turn.

So how many trips has the fly made between the car and wall?

## Homework Equations

[tex]

distance = speed * time

[/tex]

## The Attempt at a Solution

[PLAIN]http://img294.imageshack.us/img294/2922/suma.png [Broken]

A is the initial position of car. B is the position where the fly first meets the car. O is the wall.

So let x = 20km be distance from car to wall.

Let t be time taken for car to reach from A to B

Now

AB = 40t

OB = 100t

but,

x = AB + OB

t = x/140

therefore

[tex]

OB = \frac{5x}{7}

[/tex]

This is all that I got...

When I checked answers it says infinite....

I just dont get it..

Please Help!!!

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