step One
Find the total number of rocks in the gravel pit
<em>58 + 213 + 522 = 793</em>
Step Two
<em>Set up the probabilities.</em>
<em>P(Sedimentary) = 58 / 793 = 0.0731</em>
<em>P(metamorphic) = 213/ 793 =0.2686</em>
<em>P(igneous) = 522 / 793 = 0.6583</em>
Check
<em>When these are added together the answer should be one.</em>
<em>0.0731 + 0.2686 + 0.6583 = 1 just as it should.</em>