Question

In a different plan for area codes the first digit could be any number from 3 through 6 the second digit was either 5,6,7 or 8 and the third digit could be any number except 5. With this plan how many different area codes are possible?

Answer 1

144 codes are possible

Explanation:

Okay for the first digit, we shall be selecting one out of 3,4,5,6.

Meaning we are selecting one out of four choices

The number of ways this can be done is 4C1 ways = 4 ways

For the second digit, we have 5,6,7 or 8, we are still selecting 1 out of 4 selections and the number of ways we can do this is also 4 ways

And lastly , we can choose any digit for the last number expect 5 , so from 0 to 9, we are removing 1 which means we are left with 9 choices

So the number of different area codes possible are ; 9 * 4 * 4 = 144 codes