Question

you have two hourglass sand timers, one that runs for 3 minutes and another that runs for 5 minutes. How do you time 7 minutes using these two sand timers?

Answer 1

Answer:

Before starting the 7 minutes, run the 5-minute glass and 3-minute glass simultaneously until the 3-minute one ends. Then there will remain 2 minutes on the 5-minute hourglass. Now, start the time and run the 5-minute glass until it ends, then flip it over and run it again for the full 5 minutes.

Thus, we have 5 minutes minus 3 minutes to equal a beginning 2 minutes, then added to this another 5 minutes for a total of 7 minutes.

I hope this helps ^^