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Re: If a randomly selected positive single digit multiple of 3 is multipli [#permalink]
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wizardofoddz wrote:
Bunuel wrote:
If a randomly selected positive single digit multiple of 3 is multiplied by a randomly selected prime number less than 20, what is the probability that this product will be a multiple of 45?

A. 1/32
B. 1/28
C. 1/24
D. 1/16
E. 1/14


There are 4 single digit multiples of 3 --> 0,3,6,9 [Since, 0 is a multiple of 3]
There are 8 prime numbers less than 20 --> 2,3,5,7,11,13,17,19
Total number of multiplications = 8*4 = 32
Favorable outcomes = (All multiplications involving 0) AND (9*5) = 8+1 = 9 [Since, 0 is a multiple of 45]

Hence, the required probability is 9/32

Bunuel What am I getting wrong here?

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Re: If a randomly selected positive single digit multiple of 3 is multipli [#permalink]
Bunuel wrote:
If a randomly selected positive single digit multiple of 3 is multiplied by a randomly selected prime number less than 20, what is the probability that this product will be a multiple of 45?

A. 1/32
B. 1/28
C. 1/24
D. 1/16
E. 1/14


single digit multiple of 3 ; 3,6,9
prime no <20 ; 2,3,5,7,11,13,17,19
total possible products ; 3*8 ; 24
and 45 ; 9*5 ; 1 case
P ; 1/24 IMO C
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Re: If a randomly selected positive single digit multiple of 3 is multipli [#permalink]
Total =3 possibility * 8 possibility =24 possibility
Favorable = 1 possibility

So, 1/24
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Re: If a randomly selected positive single digit multiple of 3 is multipli [#permalink]
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