Question
The figure below shows the front and rear view of a disc, which is shaded with identical patterns. The disc is flipped once with respect to any one of the fixed axes 1-1, 2-2 or 3-3 chosen uniformly at random. What is the probability that the disc DOES NOT retain the same front and rear views after the flipping operation?
Options :
1
0
2/3
1/3
Answer :
2/3
Solution :
If we rotate the disc along 1-1 axis,
We get front as rear and rear as front
That means this is not our favorable outcome.
If we rotated the disc along 2-2 axis,
We do not get front as rear and rear as front.
That means disc does not retain the same and this is our favorable outcome.
If we rotated the disc along 3-3 axis,
We do not get front as rear and rear as front.
That means disc does not retain the same and this is also our favorable outcome.
After the flipping operation the probability that the disc does not retain the same front and rear view is
P(E)=Favorable outcomes/Total outcomes = 2/3
Hence, the correct option is (C).
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