Question

Four fair coins are tossed simultaneously. The probability that at least one head and at least one tail turn up is

• A. $\frac{1}{16}$
• B. $\frac{1}{8}$
• C. $\frac{7}{8}$
• D. $\frac{15}{16}$

Answer 1

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

Probability of all head or all tails appearing
= P(HHHH) + P(TTTT)

$=\frac{1}{16}+\frac{1}{16}=\frac{1}{8}$

P(at least one H and one T)
= 1 - P(all H or all T)

$=1-\frac{1}{8}=\frac{7}{8}$