6. Each of the numbers are factors of a number. What is the number? a. 1, 2, 3, 6, 9: b. 1, 2, 3, 5, 6, 15: c. 1, 2, 3, 6, 7, 21: d. 1, 2, 3, 6, 9,27:

In how many different ways can two letters be chosen from the letters A, B, C, D, E, F, and G? (The order of the two letters is not important.)

A commuter must Lrae1 from Ajax to Barrie and back every day. Four roads join the two cities. The commuter likes to vary the trip as much as possible, so she always leaves and returns by different roads. In how many different ways can she make the round-trip?