Web On Rails

You have 12 balls (of any kind), one ball either lighter or heavier than the other 11. A scale is provided to you but only three weighs are allowed. How can you possibly figure out which is the odd ball?

Bob takes the underground train to work and uses an escalator at the railway station. If Bob runs up 6 steps of the escalator, then it takes him 52.5 seconds to reach the top of the escalator. If he runs up 14 steps of the escalator, then it takes him only 32.5 seconds to reach […]