If a doctor gives you three pills, telling you to take one every half hour, how many minutes will pass from taking the first pill to the last pill?
Answer
60 minutes.
Many of you probably think that they should multiply 3 pills by 30 minutes to give 90 minutes. But think of how you take the pills. You take the first pill, and in a half-hour you take the second pill, and then in the next half-hour you take the third pill. So the number of minutes that pass from the first to the third pill is 60 minutes.