Three coins are tossed at once. What is the probability of getting at least two tails?

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Solution

Finding the probability:
When three coins are tossed at once, the sample space is $(H H H, H H T, H T H, T H H, T T H, T H T, H T T, T T T)$ .
I.e., $n (S) = 8$
Let E be the event of getting at least two tails.
So, the favorable outcomes are $(T T H, T H T, H T T, T T T)$
Thus, $n (E) = 4$
We know that $t h e p r o b a b i l i t y o f a n e v e n t = N u m b e r o f f a v o u r a b l e o u t c o m e s / T o t a l n u m b e r o f o u t c o m e s$ .
Hence, $t h e p r o b a b i l i t y o f g e t t i n g a t l e a s t t w o t a i l s = \frac{4}{8} = \frac{1}{2} .$

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