• Two trains leave from opposite ends heading towards eachother for a collision.. The distance between the two trains is 300 miles. Each train travels at 20 miles/hour. As soon as the trains set off, a bird starts flying from train A towards train B at a speed of 60 miles/h. As soon as the bird reaches train B it changes direction and heards towads train A. The bird continues to fly back and forth between the two trains uptil the last when the two trains collide and the bird gets squashed. Find the total distance travelled by the bird ?

Aside from feeling pity for the poor bird, this quesiton looks like a calculus monster. Fear not ! for this is a classical case of not being able to see the forest for the trees. Questions are often phrased and worded so as to confuse you.

If you like you can use calculus to solve this question however let's try a much easier train of thought. The bird is in flight from the time the trains start moving to the time till they collide i.e. the bird keeps flying for the time it takes for the trains to collide. So if you can find the time the trains would take to collide you are done. You multiply the time with the speed of the bird and you get the total distance the bird would have travelled before being squashed. Here's the math: