The usual average waiting time to see a doctor is one and a half hours. One doctor’s office compared their daily average waiting times to this average. On which day was the waiting time the shortest?
We are told on Monday that the waiting time was negative 35 minutes. This means it was 35 minutes less. On Tuesday, the waiting time was positive or plus one and a quarter hours. This means it was one and a quarter hours longer than the average. Finally, on Wednesday, we are told that the waiting time was negative half an hour. This means it was half an hour less than the average of one and a half hours.
As we need to calculate the shortest waiting time, we can immediately rule out Tuesday as this was positive and therefore longer than the average. We know that one hour is equal to 60 minutes. This means that half an hour is equal to 30 minutes as a half of 60 is 30. The waiting time on Wednesday was negative 30 minutes compared to the average. Taking 30 minutes or half an hour away from one and a half hours gives us one hour. This was the average waiting time on Wednesday. On Monday, we need to take 35 minutes away from one and a half hours. This gives us 55 minutes.
We can therefore conclude that Monday had the shortest waiting time of 55 minutes.