Dalia owns a gravel pit. She took a random sample of rocks and counted 58 sedimentary rocks, 213 metamorphic rocks, and 522 igneous rocks.

Use the observed frequencies to create a probability model for Dalia randomly selecting one rock from her gravel pit.

Step One

Find the total number of rocks in the gravel pit

58 + 213 + 522 = 793

Step Two

Set up the probabilities.

P (Sedimentary) = 58 / 793 = 0.0731

P (metamorphic) = 213 / 793 = 0.2686

P (igneous) = 522 / 793 = 0.6583

Check

When these are added together the answer should be one.

0.0731 + 0.2686 + 0.6583 = 1 just as it should.