If it takes one hour for the spectators to get in using 6 gates, we can calculate the rate of spectators entering per gate per hour. Let's denote this rate as
.
So,
.
Now, if we open 3 more gates, the total number of gates becomes 6 + 3 = 9 gates.
Since the rate of spectators entering per gate per hour remains the same, the total rate of spectators entering per hour will be
.
To find the time it will take for spectators to get in using 9 gates, we need to divide the total number of spectators by the rate.
Let's denote the time taken to get in using 9 gates as
.
So,
.
Therefore, it will take
hour for the spectators to get in if 3 more gates are opened, which is approximately 6.67 minutes.