If I had a three minute eggtimer and a five minute eggtimer and I need to boil an egg for seven minutes how would I do this?

Answer 1

Got a really long way to do it:

1) start both timers at the same time.
2) when the 3 minute one runs out lay the 5 minute one on its side to stop it (this gives you 2 mins left in 5 min one).
3) start the 3 min one at the same time as turning the 5 min back up to finish the remaining 2 mins.
3) when the 5 min one has finished its 2 mins, turn the 3 min on on its side (leaving 1 min one side and 2 mins the other)
4) finally you can then use the 5 min one completely, then once that runs out, turn the 3 min one so the most sand is at the top- giving you 2 mins, and 7 mins in total. Phew!

or:
buy a watch!