Three numbers are in the ratio 3:5:7. The largest number is 21. What is the difference between smallest and largest number?
Choose the correct choice from the following answers
A) 8
B) 10
C) 12
D) 14
E) 16
The three numbers are 3x, 5x, and 7x.   The largest number is 21 = 7*3, so x = 3.   The smallest number is   3*3= 
<gadget id="calculator">  3*3</gadget>
<output>9</output>
9.   21 - 9= 
<gadget id="calculator">21 - 9</gadget>
<output>12</output>
12   The answer is 12.
<result>C</result>
Three numbers are in the ratio 3:5:7. The largest number is 21. What is the difference between smallest and largest number?