A senatorial candidate had planned to visit seven cities prior to a primary election. However, he could only visit four of the cities. How many different it...

A senatorial candidate had planned to visit seven cities prior to a primary election. However, he could only visit four of the cities. How many different itineraries could be considered?

Answer Details

Number of itineraries = 7P4
=$\frac{7!}{(7-4)!}=\frac{7!}{3!}=\frac{7\times 6\times 5\times 4\times 3!}{3!}=840$