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Updated on: 10 Feb 2020, 03:03
Originally posted by QuantMadeEasy on 04 Feb 2020, 03:55.
Last edited by QuantMadeEasy on 10 Feb 2020, 03:03, edited 1 time in total.
Last edited by QuantMadeEasy on 10 Feb 2020, 03:03, edited 1 time in total.
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C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
45%
(medium)
Question Stats:
65% (01:42) correct
35%
(01:45)
wrong
based on 69
sessions
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Not Attempted Yet
Twenty-five percent of a group of students are exactly 10 years old. The students are asked one at a time their age. What is the probability that the 5th student asked is the first exactly 10 years old?
a. \(\frac{1}{4^5}\)
b. \(\frac{3^5}{4^5}\)
c. \(\frac{3^4}{4^5}\)
d. \(\frac{1}{4^4}\)*\(\frac{3}{4}\)
e. Cannot be determined
a. \(\frac{1}{4^5}\)
b. \(\frac{3^5}{4^5}\)
c. \(\frac{3^4}{4^5}\)
d. \(\frac{1}{4^4}\)*\(\frac{3}{4}\)
e. Cannot be determined
04 Feb 2020, 08:30
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The probability that the 5th student is the first 10 year old is the same as the probably that the first four are NOT 10 times the probability that the 5th is 10.
If 25% are 10, then 75% are not, so (3/4)^4 * 1/4 is the probability that the first four are not 10, and the 5th is 10
ANS) C
If 25% are 10, then 75% are not, so (3/4)^4 * 1/4 is the probability that the first four are not 10, and the 5th is 10
ANS) C
06 Feb 2020, 05:21
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Bunuel , I chose Answer E (cannot be determined) because I thought this exercise was "without replacement": Once you have picked the first student out of n students, you have n-1 students left to ask their age. Can you help explain why this is wrong? Thanks!
