Question

What is the probability that a number selected from 1,2,3.......................68,69,70, is perfect square or a perfect cube?

A 1/5 Correct Answer Incorrect Answer
B 1/10 Correct Answer Incorrect Answer
C 1/70 Correct Answer Incorrect Answer
D 1/7 Correct Answer Incorrect Answer
E None of these Correct Answer Incorrect Answer

Solution

perfect squares = 1,4,9, 16,...64 = 8 numbers perfect cubes = 1,8,27,64 = 4 numbers Favourable outcomes = 1, 4, 8, 9, 16, 25, 27, 36, 49, 64 = ( 8+ 4 -2 common) Hence No. of favourable outcomes = 10 No. of total outcomes = 70 ∴ Required probability = 10/70 = 1/7

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