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# The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday.

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Joined: 02 Sep 2009
Posts: 61302
The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday.  [#permalink]

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22 Jan 2020, 01:13
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Difficulty:

35% (medium)

Question Stats:

77% (01:19) correct 23% (00:56) wrong based on 26 sessions

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The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday. What is the probability that it rains in Dennyville on at least one of these two days?

A. 120%
B. 88%
C. 76%
D. 60%
E. 32%

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The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday.  [#permalink]

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Updated on: 22 Jan 2020, 06:48
1
Bunuel wrote:
The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday. What is the probability that it rains in Dennyville on at least one of these two days?

A. 120%
B. 88%
C. 76%
D. 60%
E. 32%

METHOD 1:

Probability of raining on Monday = 40%
Probability of raining on Tuesday = 80%

Probability on raining one atleast one of the two days = Probability of rain on Monday + Probability of Rain on Tuesday - Probability of Raining on both days

i.e. Probability on raining one atleast one of the two days = 0.40+0.80 - (0.4*0.8) = 0.88 = 88%

ALTERNATIVE METHOD-2

Probability on raining one atleast one of the two days = 1 - (Probability of not raining on both days)
Probability of NOT raining on Monday = 100-40 = 60% = 0.6
Probability of NOT raining on Monday = 100-80 = 20% = 0.2
i.e. Probability on raining one atleast one of the two days = 1 - (0.6*0.2) = 1- 0.12 = 0.88 = 88%

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Originally posted by GMATinsight on 22 Jan 2020, 01:23.
Last edited by GMATinsight on 22 Jan 2020, 06:48, edited 1 time in total.
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The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday.  [#permalink]

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22 Jan 2020, 05:51
GMATinsight ;
sir , please see highlighted part

GMATinsight wrote:
Bunuel wrote:
The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday. What is the probability that it rains in Dennyville on at least one of these two days?

A. 120%
B. 88%
C. 76%
D. 60%
E. 32%

METHOD 1:

Probability of raining on Monday = 40%
Probability of raining on Tuesday = 80%

Probability on raining one atleast one of the two days = Probability of rain on Monday + Probability of Rain on Tuesday - Probability of Raining on both days

i.e. Probability on raining one atleast one of the two days = 0.40+0.80 - (0.4*0.8) = 0.88 = 88%

ALTERNATIVE METHOD-2

Probability on raining one atleast one of the two days = 1 - (Probability of not raining on both days)
Probability of NOT raining on Monday = 100-40 = 60% = 0.2
Probability of NOT raining on Monday = 100-80 = 20% = 0.2
i.e. Probability on raining one atleast one of the two days = 1 - (0.4*0.2) = 1- 0.12 = 0.88 = 80%

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Location: India
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Re: The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday.  [#permalink]

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22 Jan 2020, 05:52
no rain monday ; .6 and for tuesday ; .2
atleast rain on 1 of the days ; 1-(.6*.2) ; 1-.12 ; .88
or say 88%
IMO B

Bunuel wrote:
The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday. What is the probability that it rains in Dennyville on at least one of these two days?

A. 120%
B. 88%
C. 76%
D. 60%
E. 32%
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Re: The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday.  [#permalink]

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24 Jan 2020, 09:29
1
Bunuel wrote:
The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday. What is the probability that it rains in Dennyville on at least one of these two days?

A. 120%
B. 88%
C. 76%
D. 60%
E. 32%

The probability that it rains on at least one day is:

P (rain at least one day) = 1 - (probability of no rain on each day)

P (rain at least one day) = 1 - 0.6 x 0.2

P (rain at least one day) = 1 - 0.12 = 0.88

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Re: The chance of rain in Dennyville is 40% on Monday and 80% on Tuesday.   [#permalink] 24 Jan 2020, 09:29
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