niketdoshi123 wrote:The probability is 1/2 that a certain coin will turn up heads on any given toss. If the coin is to be tossed three times, what is the probability that on at least one of the tosses the coin will turn up tails??
a)1/8
b)1/2
c)3/4
d)7/8
e)15/16
1-(1/2)^3= ans
Different Approach please!!
Here's a slight variation.
Total possible outcomes:
Number of options for the first toss = 2. (Heads or tails.)
Number of options for the second toss = 2. (Heads or tails.)
Number of options for the third toss = 2. (Heads or tails.)
To combine these options, we multiply:
2*2*2 = 8.
Good outcomes:
Of the 8 possible outcomes, only one outcome is BAD: HHH.
This is the only way NOT to get at least one tails.
Thus, the number of GOOD outcomes = 8-1 = 7.
Good/Total = 7/8.
The correct answer is
D.
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