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Let n=10lambda+r, where lambda,rinN, 0l...

Let ` n=10lambda+r, where lambda,rinN, 0lerle9.` A number a is chosen at random from the set {1, 2, 3,…, n} and let `p_n` denote the probability that `(a^2-1)` is divisible by 10.
If r=9, then `np_n` equals

A

`2lambda-1`

B

`2lambda`

C

`(2lambda+1)`

D

`lambda`

Text Solution

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The correct Answer is:
(c)
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