SOLUTION: On the dial of a telephone there are ten numbered holes, one of which is marked 0. If 0 is dialled first, the exchange is rung. In how many ways can a number of three digits be dia

Algebra ->  Permutations -> SOLUTION: On the dial of a telephone there are ten numbered holes, one of which is marked 0. If 0 is dialled first, the exchange is rung. In how many ways can a number of three digits be dia      Log On


   

Question 1156025: On the dial of a telephone there are ten numbered holes, one of which is marked 0. If 0 is dialled first, the exchange is rung. In how many ways can a number of three digits be dialled without ringing the exchange?
Found 2 solutions by BlGDAVE, ikleyn:
Answer by BlGDAVE(19) About Me  (Show Source):
Answer by ikleyn(52781) About Me  (Show Source):
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In this problem, the order of holes is important (does matter); 0 is prohibited at every dial; and repeating is allowed.


So, there are 9 options to chose first hole of remaining 9;

    there are 9 options to chose second hole of 9;

    there are 9 options to chose third hole of 9.


In all, there are 9*9*9 = 729 ways to dial under given conditions.    ANSWER

Solved.