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29 Oct 2018, 01:06
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E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
15%
(low)
Question Stats:
78% (00:41) correct
22%
(00:43)
wrong
based on 147
sessions
History
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Not Attempted Yet
A coin that is tossed will land heads or tails, and each outcome has equal probability. What is the probability that the coin will land heads at least once on two tosses?
A. 1/4
B. 1/3
C. 1/2
D. 2/3
E. 3/4
A. 1/4
B. 1/3
C. 1/2
D. 2/3
E. 3/4
29 Oct 2018, 05:15
Kudos
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The probability of at least one heads in two flips = 1 - probability of no heads
Probability of no heads in both flips = 1/2 * 1/2 (both are tail)
so 1 - 1/4 = 3/4
Or we can do it in the longer way
One heads, one tails = 1/2 * 1/2 = 1/4
One tail and one heads = 1/2 * 1/2 = 1/4
Two heads = 1/2 * 1/2 = 1/4
Add them we get 3/4
Answer choice E
Probability of no heads in both flips = 1/2 * 1/2 (both are tail)
so 1 - 1/4 = 3/4
Or we can do it in the longer way
One heads, one tails = 1/2 * 1/2 = 1/4
One tail and one heads = 1/2 * 1/2 = 1/4
Two heads = 1/2 * 1/2 = 1/4
Add them we get 3/4
Answer choice E
29 Oct 2018, 05:49
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Bunuel
Total outcomes when a coin is tossed twice = 2*2 = 4
METHOD 1:
Case 1: Exactly 1 Head outcomes will be HT or TH i.e. 2 outcomes
Case 2: Exactly 2 Head outcomes will be HH i.e. 1 outcome
Favourable Outcomes = 3
Probability = 3/4
METHOD 2:
Unfavourable case is when None of the toss results in a Head i.e. Both Tails i.e. TT i.e. 1 outcome
Unfavourable Probability = 1/4
Favourable Probability = 1- Unfavourable probability = 1- (1/4) = 3/4
Answer: Option E
