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# Peter rolls two dice at the same time. What is the probabili

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Peter rolls two dice at the same time. What is the probabili [#permalink]

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28 Apr 2014, 01:32
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Peter rolls two dice at the same time. What is the probability that he will roll a double?

a) 1/12

b) 1/36

c) 1/6

d) 5/12

e) 1/3
[Reveal] Spoiler: OA
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Joined: 02 Sep 2009
Posts: 44351
Re: Peter rolls two dice at the same time. What is the probabili [#permalink]

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28 Apr 2014, 01:36
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tusharGupta1 wrote:
Peter rolls two dice at the same time. What is the probability that he will roll a double?

a) 1/12

b) 1/36

c) 1/6

d) 5/12

e) 1/3

The number of total outcomes = 6*6 = 36;

The number of favorable outcomes = 6: {1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}.

The probability = 6/36 = 1/6.

Hope it's clear.
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Re: Peter rolls two dice at the same time. What is the probabili [#permalink]

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01 Oct 2015, 04:34
We can have 6 different outcomes on a dice.
Total outcomes on two dices = 6*6

We need only the cases when Peter rolls a double, that means only the outcomes in which the numbers on both the dices are same

They can be {1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}.
A total of 6 outcomes

Probability = favorable outcomes/ total outcomes = 6/36 = 1/6.

Option C
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Re: Peter rolls two dice at the same time. What is the probabili [#permalink]

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12 Mar 2017, 20:02
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tusharGupta1 wrote:
Peter rolls two dice at the same time. What is the probability that he will roll a double?

a) 1/12

b) 1/36

c) 1/6

d) 5/12

e) 1/3

Hi,
My approach was as below:

Probability of getting any number from the 1st dice = 1
Probability of getting the same no. from the 2nd dice = $$\frac{1}{6}$$

Overall Probability = $$1*\frac{1}{6}$$ = $$\frac{1}{6}$$
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Re: Peter rolls two dice at the same time. What is the probabili [#permalink]

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13 Mar 2017, 00:37
The number of total outcomes = 6*6 = 36;

favourable outcomes = 6: {1, 1}, {2, 2}, {3, 3}, {4, 4}, {5, 5}, {6, 6}.
probability = 6/36 = 1/6.

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Re: Peter rolls two dice at the same time. What is the probabili [#permalink]

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15 Nov 2017, 13:11
Expert's post
Top Contributor
tusharGupta1 wrote:
Peter rolls two dice at the same time. What is the probability that he will roll a double?

a) 1/12

b) 1/36

c) 1/6

d) 5/12

e) 1/3

Notice that the probability doesn't change if we roll one die first and the other die second. So, let's do this.

Let die #1 the first die, and let die #2 be the second dice

P(both dice are the same) = P(die #1 is any value AND die #2 matches die #1)
= P(die #1 is any value) x P(die #2 matches die #1)
= 1 x 1/6
= 1/6
= C

ASIDE: Some people might wonder how I found the first probability to equal 1.
We need to recognize that the first die can be any value and, in order to get a double, the second guy must match the first die.
Once we have rolled the first die, there is a probability of 1/6 that the second die matches the first die.

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Re: Peter rolls two dice at the same time. What is the probabili   [#permalink] 15 Nov 2017, 13:11
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