ProbabilityMedium
Question
Two distinct numbers a and b are selected at random from $1,2,3,\ldots\ldots,50$. The probability, that their product ab is divisible by 3 , is
Options
A.$\frac{561}{1225}$
B.$\frac{664}{1225}$
C.$\frac{272}{1225}$
D.$\frac{8}{25}$
Solution
Req. probability $= 1$ - (product not divisible by 3 )
Multiple of $3 = 16$
Not multiple of $3 = 34$
$$= 1 - \frac{\ ^{34}C_{2}}{\ ^{50}C_{2}} = \frac{664}{1225}$$
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