The forth proportional to 10,8,15 is?  Pick: A) 15 B) 12 C) 18 D) 20 E) 24
Let the fourth proportional to 10,8,15 be x   then 10:8::15:x   10x = 8*15   x = 12   Answer is 12
<result>B</result>
The forth proportional to 10,8,15 is?