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in Mathematics by (70.5k points)

If n integers taken at random are multiplied together, then the probability that the last digit of the product is 1, 3, 7 or 9 is_______ 

(a) (2n/5n)

(b) [(4n – 2n)/5n]

(c) (4n/5n)

(d) (2/5)

1 Answer

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Best answer

The correct option (a) (2n/5n)  

Explanation:

Last digit can be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.

∴ Number of ways of choosing last digit = 10n

given: last digit be 1, 3, 7, 9. (none of it is even or 0 or 5)

we have choice of 4 digit i.e. 1, 3, 7, 9 with each n numbers should end.

∴ favourable number of ways = 4n

∴ probability = (4n/10n) = (2/5)n.

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