Problema Solution

how can you cook soemthing for exactly 13 minutes if all you have are a 5-minute and a 9 minute egg timer?

Answer provided by our tutors

Well, you could run the 5-minute timer over 3 consecutive periods while running the 9-minute timer concurrently for 2 consecutive periods... start cooking after the first period of 5-minutes and then restart the 5-minute timer for two more periods:
(2*9-3*5)+2*5

click here to simplify

13