Step 1 :First, we need to calculate the total number of vehicles at Bob's Auto Plaza. There are 14 new cars, 3 used cars, and 6 new trucks. So, the total number of vehicles is \(14 + 3 + 6 = 23\).
Step 2 :Next, we need to find out the number of vehicles that are either used or a truck. There are 3 used cars and 6 trucks, so the total number of vehicles that are either used or a truck is \(3 + 6 = 9\).
Step 3 :The probability of an event is calculated by dividing the number of favorable outcomes by the total number of outcomes. In this case, the favorable outcomes are the vehicles that are either used or a truck, and the total outcomes are all the vehicles.
Step 4 :So, the probability that the vehicle Bob chooses is either used or a truck is \(\frac{9}{23} = 0.391304347826087\).
Step 5 :Rounding this to the nearest hundredth, we get \(0.39\).
Step 6 :So, the probability that the vehicle Bob chooses is either used or a truck is approximately \(\boxed{0.39}\).