A Matter of Time

She starts by turning over both timers togther, but not yet putting the egg in the water. When the 3 minute timer finishes, she puts the egg in the water and turns the 3 minute timer again (Egg: 0 minutes. From start: 3 minutes). After that next 3 minutes, she turns the 3 minute timer again. (Egg: 3 minutes. From start: 6 minutes). After one more minute, the 7 minute timer will finish (Egg: 4 minutes. From start: 7 minutes). At that point, one minute’s worth of sand has gone through the 3 minute timer, so if Emily now flips this back over, it will take one minute to empty back into the bottom half (Egg: 5 minutes. From start: 8 minutes).  Emily has had to wait 8 minutes, but she has a perfect 5 minute egg.