Pls help me

[tracyyahoo]

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

The way I approach this is (first toss will 1/1 is 1. (seocond toss) will be 1/2
so 1*1/2 is 1/2

OA is E ,why

[shankar.ashwin]

P(atleast one head) = 1 - P(both tails)

= 1 -(1/2)(1/2) = 3/4

[VivianKerr]

The keyword here is "at least". It could land on head the 1st time, the 2nd time, or BOTH times. Since there are only 2 outcomes and 2 tosses, it's easy to list the possibilities:

HH
TT
TH
HT

Notice how 3 out of the 4 possibilities include an "H." That is why it is 3/4.