logical problem for finding the probability [closed]

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hi to all

I want to know how to find the solution for this problem. consider in a Jar there are 10 papers numbered 1 to 10. we have to take 2 papers from that. what is the probability that 2 numbers are consecutive numbers.

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It's a probability to choose one of 9 consecutive pairs from C(10, 2) possible pairs. Thus its 9 / (10*9 / 2) = 1 /5

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The probability of getting 2-8 is 8/10. Once we have a given number in that range, the probability of getting one of the two adjacent numbers is 2/9. 8/10 * 2/9 = 16/90.

The probability of getting either a 1 or a 10 is 2/10. If we have one of those two endpoint numbers, the probability of getting the one adjacent number is 1/9. 2/10 * 1/9 = 2/90.

Adding these together, we have a total probability of 18/90 or 1/5.

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Your first choice has ten possible numbers. 8 of those 10 will have two consecutive numbers, while the other two only have 1. Your second choice will be out of nine numbers. So

(8/10 * 2/9) + (2/10 * 1/9) = 9/45 = 1/5