how can a chef use a 13-minute hourglass and a 5-minute hourglass to time vegetables that must steam for 21 minutes

Answer 1

To time the vegetables that must steam for 21 minutes using a 13-minute hourglass and a 5-minute hourglass, the chef can follow the steps below:

1. Start both the 13-minute and 5-minute hourglass simultaneously.
2. Once the 5-minute hourglass is empty, flip it again immediately.
3. Allow the 13-minute hourglass to run until it finishes and empties completely.
4. At this point, the 5-minute hourglass will have been running for 8 minutes (13 minutes - 5 minutes).
5. Flip the 5-minute hourglass as soon as the 13-minute hourglass is empty.
6. Allow the 5-minute hourglass to run until it empties completely.
7. Now, the total time that has passed since starting both hourglasses is 13 minutes + 8 minutes = 21 minutes.
8. As the vegetables had to steam for exactly 21 minutes, the chef can now remove them from the heat.

By combining the time measurements of the two hourglasses and taking advantage of the extra time provided by the 5-minute hourglass, the chef can accurately time the vegetables to steam for 21 minutes.