8. Social Security numbers assigned in Michigan begin with the number 3. The second number must be 6, 7, or 8. The other 7 digits can be any digit. Find the number of possible Michigan Social Security num- bers.

EXPERT ANSWER

s it is mention that first place can be filled by number 3 only..

So, First place can be filled by only one choice..

For 2nd place we have choices of numbers are 6, 7 and 8 …

Threfore, 2nd place have 3 choices

And there is no condition mention, so all other 7 places, we have total 10 choices for each places..

Therefore..

Total number of ways = 1*3*10^7 = 30000000