2) You have two egg-timers. One takes 11 minutes for the sand to run through and the other takes 7 minutes. You want to boil an ostrich egg for 15 minutes. How can you measure exactly 15 minutes with your two egg-timers?

To measure exactly 15 minutes using the 11-minute and 7-minute egg-timers, you can follow these steps: 1. Start both the 11-minute and 7-minute egg-timers at the same time. 2. When the 7-minute timer runs out, 7 minutes have passed. At this point, the 11-minute timer has 4 minutes left (11 - 7 = 4). 3. Immediately flip the 7-minute timer to start it again. 4. When the 11-minute timer runs out (after 4 more minutes), a total of 11 minutes have passed. At this point, the 7-minute timer has been running for 4 minutes (7 - 4 = 3 minutes left). 5. Immediately flip the 7-minute timer again. 6. When the 7-minute timer runs out this time, 3 more minutes have passed, making a total of 14 minutes (11 + 3 = 14). 7. Immediately flip the 7-minute timer one last time. 8. When the 7-minute timer runs out again, 1 more minute will have passed, making a total of 15 minutes. Now you have successfully measured exactly 15 minutes!