Question

three unbiased coins are tossed. what is the probability of getting one head or two heads?

Answer 1

When three unbiased coin are tossed together, then

the sample space obtained = {HHH, HHT, HTH, HTT, THH, THT, TTH, TTT}

where H means the head appears and T means the tail appears.

∴Total number of outcomes is obtained when three unbiased coins are tossed=8

Now,

a) The outcomes of the event, getting exactly one head or two heads = {HHT, HTH , THH, HTT, THT, TTH}

∴ Number of outcomes of the event getting either 1 head or 2 heads by tossing three unbiased coins =6

$\mathrm{required}\mathrm{probability}=\frac{\mathrm{no}.\mathrm{of}\mathrm{favourable}\mathrm{outcomes}}{\mathrm{total}\mathrm{number}\mathrm{of}\mathrm{possible}\mathrm{outcomes}}=\frac{6}{8}=\frac{3}{4}$