Question

What is the theoretical probability of a coin landing tails up?

Answer 1

Answer: 1:2

Explanation:

Answer 2

The probability that a fair coin lands tail up is 1/2, which is equal to 0.5.

Explanation:

There are two possible outcomes when a coin is flipped (saving for the case when the coin lands on its side.)

1. The coin lands head-up;
2. The coin lands tail-up.

If the coin is fair, the two outcomes should be equally likely. In that case, apply the following formula:

`\begin{aligned}&\text{Probability that the coin lands tail-up}\\ =&\frac{\text{Number of outcomes that the coin lands tail-up}}{\text{Total Number of equally-likely possible outcomes}}\\=&(1)/(2) \\=& 0.5 \end{aligned}`.

Credit for the phrasing of this probability formula goes to the Khan Academy article "Probability: the basics".