Answer: 1/27
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Step-by-step explanation:
2/3 is the probability of passing a test, so 1/3 is the probability of failing
Note how 2/3 and 1/3 add to 3/3 = 1 to represent 100%
The probability of failing 3 tests in a row is (1/3)^3 = (1/3)*(1/3)*(1/3) = 1/27 assuming each test event is independent from one another.
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Side note: the probability of passing at least one test is 1-1/27 = 26/27 and the probability of passing all three tests in a row is (2/3)^3 = 8/27