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# in a leap year, find the probability that there are exactly

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Manager
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in a leap year, find the probability that there are exactly  [#permalink]

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Updated on: 08 Mar 2018, 11:52
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63% (01:31) correct 38% (00:54) wrong based on 48 sessions

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In a leap year, find the probability that there are exactly 5 Mondays in the month of September?

a. 1/7
b. 2/7
c. 3/7
d. 4/7
e. 5/7

Originally posted by kanakdaga on 08 Mar 2018, 10:38.
Last edited by pushpitkc on 08 Mar 2018, 11:52, edited 1 time in total.
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Re: in a leap year, find the probability that there are exactly  [#permalink]

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08 Mar 2018, 11:57
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1
kanakdaga wrote:
In a leap year, find the probability that there are exactly 5 Mondays in the month of September?

a. 1/7
b. 2/7
c. 3/7
d. 4/7
e. 5/7

Since there are 30 days in the month of September, there are exactly 4 weeks and 2 extra days.

There are 2 possibilities that the month will have 5 Mondays.
1. When the first day is a Monday(1,8,15,22,29)
2. When the first day in a Sunday(2,9,16,23,30)

Therefore, the probability that there are exactly 5 Mondays is $$\frac{2}{7}$$(Option B)
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Re: in a leap year, find the probability that there are exactly  [#permalink]

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08 Mar 2018, 22:17
September month has 30 days. Out of which the probability of having 5 monday's will occur only 2 conditions. Either the week starts with Sunday or week starts with Monday.

There are 2 possibility out of 7.

Ans: Option B - 2/7
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Re: in a leap year, find the probability that there are exactly  [#permalink]

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13 Mar 2018, 10:23
1
kanakdaga wrote:
In a leap year, find the probability that there are exactly 5 Mondays in the month of September?

a. 1/7
b. 2/7
c. 3/7
d. 4/7
e. 5/7

Good question. Took me some time to figure it out.

Since September has 30 days then it will have 5 Mondays only if the 1st day of the month is a Monday or a Sunday.

Hence the probability is 2/7. So B.
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Re: in a leap year, find the probability that there are exactly  [#permalink]

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15 Mar 2018, 04:47
rohan2345 wrote:
kanakdaga wrote:
In a leap year, find the probability that there are exactly 5 Mondays in the month of September?

a. 1/7
b. 2/7
c. 3/7
d. 4/7
e. 5/7

Good question. Took me some time to figure it out.

Since September has 30 days then it will have 5 Mondays only if the 1st day of the month is a Monday or a Sunday.

Hence the probability is 2/7. So B.

Sorry, but how is the total possible outcome 7, is it possible for a month to have 7 Mondays .
So 2 Mondays out of 7 hence 2/7 ?
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Re: in a leap year, find the probability that there are exactly  [#permalink]

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15 Mar 2018, 04:58
1
stne wrote:

Sorry, but how is the total possible outcome 7, is it possible for a month to have 7 Mondays .
So 2 Mondays out of 7 hence 2/7 ?

Hey stne ,

No, you didn't understand the solution properly.

What we are saying is inorder to have 5 Mondays we need to have 1st day of the month either a Monday or a Sunday.

Now, Probability = Number of favourable outcomes/Total number of outcomes.

Number of favourable outcomes (1st day as Monday or Sunday) = 2
Total number of outcomes(1st day could be any of the 7 days) = 7

Hence, Probability = 2/7.

Does that make sense?
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Re: in a leap year, find the probability that there are exactly  [#permalink]

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15 Mar 2018, 05:01
It ddefinitely has to be option B. That is my answer.
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Re: in a leap year, find the probability that there are exactly  [#permalink]

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15 Mar 2018, 06:25
abhimahna wrote:
stne wrote:

Sorry, but how is the total possible outcome 7, is it possible for a month to have 7 Mondays .
So 2 Mondays out of 7 hence 2/7 ?

Hey stne ,

No, you didn't understand the solution properly.

What we are saying is inorder to have 5 Mondays we need to have 1st day of the month either a Monday or a Sunday.

Now, Probability = Number of favourable outcomes/Total number of outcomes.

Number of favourable outcomes (1st day as Monday or Sunday) = 2
Total number of outcomes(1st day could be any of the 7 days) = 7

Hence, Probability = 2/7.

Does that make sense?

Yes now its clear, thanks a ton.
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Re: in a leap year, find the probability that there are exactly   [#permalink] 15 Mar 2018, 06:25
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