The fourth proportional to 5, 8, 15 is:	Choices:  A) 20  B) 22  C) 24  D) 21  E) 23
Let the fourth proportional to 5, 8, 15 be x.   Then, 5 : 8 : 15 : x   = 5x = (8 x 15)   x = (8 x 15)/5= 24.   Answer is 24.
<result>C</result>
The fourth proportional to 5, 8, 15 is: