I am writing down a probability problem which i faced during one of my CATs. For me probability is always a nightmare and if this kind of question gonna be present in the actual GMAT then God knows what will happen to me!!! Anyways, try giving the solution to this one.
Problem:
A fair coin with sides marked heads and tails is to be tossed eight times. What is the probability that the coin will land tails side up more than five times?
Options:
1) 37/256 2) 56/256 3) 65/256 4) 70/256 5) 81/256
I know Arun would be laughing at me ;) I know Arun (and for that matter any Engineer in our class) can do this problem with ease...
Would request everyone to share their own short-cut methods to crack maths/DS problems. This will surely help us to learn more in a limited time... I am waiting for your comments for this posting...
All the best guys/gals.
2 comments:
Know its too late to reply.
for such problems always use
(p+1-p)^n
where p= prob of event happening
1-p = complement of the event happening
for toss p=1/2
according to question we need to find prob of getting more than 5 heads
8C6(0.5)^6*(0.5)^2+
8C7(0.5)^7*(0.5)^1+
8C8(0.5)^8*(0.5)^0
=(28+8+1)/2^8=37/256
:-)
Sorry n= no of times the event is happening
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