You have the misfortune to own an unreliable clock. This one loses exactly 30 minutes every hour. It is now showing 4.00am and you know that is was correct at midnight, when you set it. The clock stopped five hours ago, what is the correct time now?
If you have a very tight nut on a bolt, what is the best way to free it:
Heat it, cool it, either, neither?
Hint: Do things get larger or smaller when you heat them?
Answer: Heat it.
The nut will increase in size more than the bolt, this makes the hole in the nut larger so freeing the joint.
I once cashed a cheque at the bank. I had spent £2.84 before I realised the bank clerk had made a mistake. He had transposed the pounds with the pence. I now had exactly 5 times the value of the original cheque. What was the original cheque's value?