Multiply the number of choices for each position together. Three of the numbers can be repeated with the one (5) only being used once.
(4 possible choices) × (3 possible choices) × (3 possible choices) × (3 possible choices) = 4 × 3 × 3 × 3 = 108
The answer is 2.5 cm
First, you multiply 4 and 12, and you get 48
Then you take 120 and you divide it by 48.
This leaves you with 2.5
To check you multiply 2.5, 4, and 12
6P3 => 6!/(6-3)! = 120.
I can't very well explain, but I hope it works.
