Question 169954
<font size = 7 color = "red"><b>Edwin's solution:</b></font>
Two trains 100 km apart each travel towards each other at 10 km per hour. A bumblebee starts flying back and forth between the two trains at 60 km per hour, until the two trains crash into each other. How far does the bumblebee travel? 
<pre><font size = 4 color = "indigo"><b>

You can do it in your head:

The trains are approaching each other at a rate
of 10+10 or 20 km/h.  So their distance apart, which
is 100 km, will shrink to 0 in 5 hours.  So the 
bumblebee will fly for 5 hours at 60 km per hour, 
so it will fly a total of 300 km before it gets 
squished between the two trains.

Edwin</pre>