A, B and C start swimming in a pool simultaneously from the same end. To complete 10 laps, A takes 10 minutes, B takes 8 minutes and C takes 4 minutes. What is the ratio of speeds A:B:C?  Choose the correct choice from the following choices:
A) 3:4:5
B) 12:15:20
C) 5:4:3
D) 4:5:10
E) 12:15:25
The slowest one is A, then comes B and the fastest one is C. So, the the ratio of speeds A:B:C must be in ascending order. Eliminate options C, D, and E.   A's speed (distance)/(time) = 10/10= 
<gadget id="calculator">10/10</gadget>
<output>1</output>
1 lap per minute= 4laps in 4 minute;   B's speed (distance)/(time) = 10/8 = 5/4 lap per minute = 5 laps in 4 minutes;   C's speed (distance)/(time) = 10/4 = 5/2 lap per minute = 10 laps in 4 minutes/   Therefore, the the ratio of speeds A:B:C is 4: 5:10.   Answer: 4:5:10.
<result>D</result>
A, B and C start swimming in a pool simultaneously from the same end. To complete 10 laps, A takes 10 minutes, B takes 8 minutes and C takes 4 minutes. What is the ratio of speeds A:B:C?