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# Final mathematics exam

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The final mathematics exam at a certain school contains questions of equal difficulty and is matched to the students' past performance in mathematics. Four students who take the exam have averages 25%, 50%, 60%, and 80%. What is the probability that at least one of these students will get the first question on the exam correct?

A) 97/100

B) 9/10

C) 17/20

D) 13/15

E) 23/30

jonathanxu999  Jan 13, 2018

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The probability that none get it right is q = (1-0.25)*(1-0.5)*(1-0.6)*(1-0.8) or q = (3/4)*(1/2)*(4/10)*(2/10) → 3/100

Hence the probability that at least one gets it right is p = 1 - q or p = 1 - 3/100 → 97/100

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Alan  Jan 14, 2018
Sort:

#1
+26399
+1

The probability that none get it right is q = (1-0.25)*(1-0.5)*(1-0.6)*(1-0.8) or q = (3/4)*(1/2)*(4/10)*(2/10) → 3/100

Hence the probability that at least one gets it right is p = 1 - q or p = 1 - 3/100 → 97/100

.

.

Alan  Jan 14, 2018

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