Question 431284: What is the probability that a random 2 digit number is a multiple of 7? Found 2 solutions by stanbon, robertb:Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website! What is the probability that a random 2 digit number is a multiple of 7?
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# of 2-digit numbers: 99-10+1 = 90
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# that are a multiple of 7
7*2,7*3,...,7*12
11 such numbers
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P(a random 2-digit number is a multiple of 7) = 11/90
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Cheers,
Stan H.
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You can put this solution on YOUR website! Without loss of generality, assume only positive integers. There are 90 2-digit positive integers, while there are 13 2-digit positive integers divisible by 7.
Hence the probability is 13/90.
Why 13 2-digit positive integers divisible by 7?
98 = 14 + (n-1)7, from the arithmetic sequence formula.
==> 84 = (n-1)7
==> 12 = n-1
==> n = 13.
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