JAMB - Mathematics (2007 - No. 4)
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?
640
840
520
920
Giải thích
Number of itineraries = 7P4
=\(\frac{7!}{(7-4)!}\\
=\frac{7!}{3!}\\
=\frac{7 \times 6 \times 5 \times 4 \times 3!}{3!}\\
=840\)
=\(\frac{7!}{(7-4)!}\\
=\frac{7!}{3!}\\
=\frac{7 \times 6 \times 5 \times 4 \times 3!}{3!}\\
=840\)