Question

Find the probability of getting at least 1 Head, if 3 coins are tossed.

• A. $\frac{3}{8}$
• B. $\frac{7}{8}$
• C. $\frac{1}{8}$
• D. $\frac{1}{2}$

Answer 1

The correct option is B $\frac{7}{8}$

In tossing of 3 coins once, the sample space has 8 outcomes.
{HHH, HHT, HTH, THH, TTT, THT, TTH, HTT}
∴ P (getting at least one Head) = P (getting 1or 2 or 3 Head)
= 1 − P ( getting 0 Head)
= 1 − P (getting tail in all the coins TTT) ---(1)

∴ P (getting tail in all threee coins )
$=\frac{1}{8}$

Substituting this value in (1),
P (at least one Head) $=1-\frac{1}{8}=\frac{7}{8}$