Question

Harold tosses a nickel four times. The probability that he gets at least as many heads as tails is

$\dfrac{5}{16}$

$\dfrac{3}{8}$

$\dfrac{1}{2}$

$\dfrac{5}{8}$

$\dfrac{11}{16}$

Answer: E

Concepts:binomial probability combinations

Difficulty rating: 1550

Solution:

There are $2^4=16$ equally likely outcomes for four coin tosses.

At least as many heads as tails means getting $2$ , $3$ , or $4$ heads. The number of such outcomes is $\begin{aligned} &\binom{4}{2}+\binom{4}{3}+\binom{4}{4} \\ &\quad {}=6+4+1=11. \end{aligned}$

Thus the probability is $\dfrac{11}{16}$ .

Thus, E is the correct answer.

2002 AMC 8 Problem 21

Answer: E

Difficulty rating: 1550

Solution:

Problem 21 in Other Years