How many possible tripeptides can be made with the amino acids: tyrosine,histidine,and cysteine,each used only once?

Question

Quizplus · Accepted Answer

To find the number of possible tripeptides from three distinct amino acids used exactly once, we use the formula nPr/(r!), where n is the number of distinct amino acids, and r is the number of amino acids in each peptide. 
For this problem, n=3 and r=3, so the formula gives us 3P3/(3!) = 6. Therefore, there are 6 possible tripeptides that can be made using tyrosine, histidine, and cysteine exactly once. 
Thus, the answer is choice letter C.

How Many Possible Tripeptides Can Be Made with the Amino