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# Two stacks of ten cards each are numbered 1-10 and randomly

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Senior Manager
Joined: 20 May 2014
Posts: 282
Followers: 18

Kudos [?]: 50 [0], given: 220

Two stacks of ten cards each are numbered 1-10 and randomly [#permalink]  29 Oct 2017, 02:15
00:00

Question Stats:

37% (02:08) correct 62% (00:35) wrong based on 8 sessions
Two stacks of ten cards each are numbered 1-10 and randomly shuffled. Sam has to pick the top card from each stack and guess the number on each card. What is the probability that Sam guesses both numbers correctly?

A. 0.001
B. 0.025
C. 0.01
D. 0.02
E. 0.50

Kudos for correct solution.
[Reveal] Spoiler: OA
Director
Joined: 03 Sep 2017
Posts: 521
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Kudos [?]: 343 [1] , given: 66

Re: Two stacks of ten cards each are numbered 1-10 and randomly [#permalink]  30 Oct 2017, 09:29
1
KUDOS
The probability of correctly guessing two cards from two decks of 10 cards consequently is $$\frac{1}{10}\frac{1}{10} = \frac{1}{100} = 0.01$$.

Manager
Joined: 01 Nov 2018
Posts: 82
Followers: 0

Kudos [?]: 36 [0], given: 20

Re: Two stacks of ten cards each are numbered 1-10 and randomly [#permalink]  05 Jan 2019, 01:23
Expert's post
Just remember, both stacks are separate from one another. which means that their probabilities are independent.
This is equivalent to flipping a coin at the same time as rolling a dice.
you just multiply the probabilities together.
1/10*1/10= .01
Re: Two stacks of ten cards each are numbered 1-10 and randomly   [#permalink] 05 Jan 2019, 01:23
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