if a different plan for area codes the first digit coupd be

if a different plan for area codes the first digit coupd be any number from 1 to 7 the second digit was either 4 5 or 6 and the third digit could be any number except 1 or 5 with this plan how many different area codes are possibile

Solution

We have given for first digit:any number from 1 to 7

Therefore, first digit has 7 ways.

second digit has only 3 possible ways.

Third digit has only 2 possible choice.

Lets use here multplication rule we get,

7 *4 * 2 = 56 ways or 56 different codes are possible.