SOLUTION: a two digit number is formed using digits 3,4,5,6 and 7 without replacement.what is the probability that the number is a multiple of 3.

Algebra ->  Probability-and-statistics -> SOLUTION: a two digit number is formed using digits 3,4,5,6 and 7 without replacement.what is the probability that the number is a multiple of 3.      Log On


   

Question 550207: a two digit number is formed using digits 3,4,5,6 and 7 without replacement.what is the probability that the number is a multiple of 3.
Answer by TutorDelphia(193) About Me  (Show Source):
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There are 20 possible outcomes (you have 5 choices for the first digit and 4 for the second 5*4=20):
34 no
35 no
36 yes
37 no
43 no
45 yes
46 no
47 no
53 no
54 yes
56 no
57 yes
63 yes
64 no
65 no
67 no
73 no
74 no
75 yes
76 no
Desired outcomes are multiples of 3. The quick way to see if something is a multiple of 3 is to see if its digits add up to a multiple of 3 (its a math trick). See the yes and no's above for which ones are multiples of 3.
So the ones we want are 6 and the total is 20
so 6/20 reduces to 3/10