Hey
dave13RULE: The probability of an event occurring can never be greater than 1.
So, whenever during the course of a problem you get a number
greater than 1 for a probability, be assured that you have made a mistake!
You need to multiply the probability when the events are to occur simultaneously, or consecutively.
For example, when we get three heads,
the probability will be \(\frac{1}{2}*\frac{1}{2}*\frac{1}{2} = \frac{1}{8}\).
We need to add probabilities when the events are alternatives.
For example, when there are three cases that can happen.
You can get HHT, HTT, TTT(for the three coins problem) as possible options for at least one tail.
In order to get the final answer, you need to add the individual probabilities for all the three cases.
Coming back to the problem
An easy way to solve this question is to find the probability that no tail
turns up and reduce that from 1(the maximum probability that an event can occur)
The probability that a tail does not turn up when three coins are tossed is when we get a head
on each of these coin tosses, which is \(\frac{1}{2}*\frac{1}{2}*\frac{1}{2} = \frac{1}{8}\)
Probability (atleast one tail turns up) = 1-P(All heads) = \(1 - \frac{1}{8} = \frac{7}{8}\)
(Option D)Hope this helps you!
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