The rate of spin of a certain gyroscope doubled every 10 seconds from the moment a particular stopwatch started. If after a minute and a half the gyroscope reached a speed of 800 meters per second, what was the speed, in meters per second, when the stopwatch was started?  Choose the correct choice from the following choices
A) 25/3 B) 25/4 C) 25/8 D) 25/16 E) 25/32
Let x be the original speed when the stopwatch was started.   In 90 seconds, the speed doubled 9 times.   2^9 * x = 800   x = (2^5 * 25) / 2^9 = 25/16   The answer is 25/16.
<result>D</result>
The rate of spin of a certain gyroscope doubled every 10 seconds from the moment a particular stopwatch started. If after a minute and a half the gyroscope reached a speed of 800 meters per second, what was the speed, in meters per second, when the stopwatch was started?