A doctor gives you three pills telling you to take one every half hour. How many minutes would the pills last?

The correct answer is 60 minutes. You take the first pill at 0 minutes, the second at 30 minutes, and the third at 60 minutes. The duration from the first pill to the last pill is 60 minutes (1 hour). Many people mistakenly think 30 minutes × 3 pills = 90 minutes, but that's incorrect logic. There are only 2 intervals between 3 pills, so 2 × 30 = 60 minutes.