Do you Know probability ? 2

Probability Level 3

Four numbers are multiplied together. Then , the probability that the product will be divisible by 5 or 10 is

133/625 399/625 369/625 123/625

Keshav Tiwari by Keshav Tiwari , 23, India

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1 solution

Jerry Zhuang
Jan 17, 2015

We find the probability by subtracting its negative from 1. (P(A) +P(not A) = 1) The probability that any 4 numbers' product is not divisible by 5 or ten is 4/5 to the fourth (1/5 of all the integers are divisible by 5, we don't want any of these numbers). So, we subtract that probability (256/625 from 625/625, getting 369/625.

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Right ! Upvoted ! :D

Keshav Tiwari - 6 years, 4 months ago

Did the same. P(div by 5) = 1 - P(not div by 5). Out of every 5 numbers, 4 are non-divisible by 5. So 1 - (256/625) :)

Nice question.

Ayan Jain - 6 years, 3 months ago

from where 256 had come??

sakshi rathore - 5 years, 11 months ago

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