### Home > CCG > Chapter 12 > Lesson 12.1.1 > Problem12-8

12-8.

Before there were radios and satellite communication systems, ships would communicate with each other by using a string of colored flags. With four blue flags and two red flags, how many six flag signals are possible?

Use combinations or refer back to the math notes box in Lesson 10.3.3.

$\frac{6!}{(4!)2! }=15$