Question

hilda has a fair 20 - sided polyhedron die, numbered 1 through 20. she rolls it 300 times. predict the approximate number of times hilda expects to roll a number that is 18 or greater.

Explanation:

Step1: Calculate probability of rolling 18 or greater

The numbers 18, 19, 20 are 3 out of 20 possible outcomes. So the probability $P$ of rolling a number 18 or greater on a single roll is $P=\frac{3}{20}$.

Step2: Calculate expected number of times

The expected - value formula is $E = n\times P$, where $n$ is the number of trials. Here, $n = 300$ and $P=\frac{3}{20}$. So $E=300\times\frac{3}{20}$.
$300\times\frac{3}{20}=\frac{300\times3}{20}=\frac{900}{20}=45$.

Answer:

45