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If the four positive integers are se...

If the four positive integers are selected randomly from the set of positive integers, then the probability that the number 1,3, 7 and 9 are in the unit place in the product of 4 - digit, so selected is

A

` (7 ) /(625 ) `

B

` (2 ) /( 5 ) `

C

` (5 )/( 625 ) `

D

` (16 )/( 625 ) `

Text Solution

Verified by Experts

The correct Answer is:
D
The number of digits on unit place of any number = 10
` therefore " " n ( S) = 10 `
The necessary condition for becoming the digits 1, 3, 5 or 7 at the unit place of product of four numbers that the digits 1, 3 , 5 or 7 at unit place of every number.
` therefore n ( A) = 4 `
` therefore P ( A) = ( 4 ) /( 10 ) = ( 2 ) /( 5 ) `
So, required probability = ` ((2 )/( 5))^ 4 = (16 ) /( 625 ) `
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