Watch Gaining TimeDate: 11/10/2002 at 00:18:24 From: Ann Subject: Watch gaining time A watch gains six minutes every hour. If the time of this watch is set accurately at midnight, and the watch now shows 8:26 a.m., if the watch stopped 30 minutes ago, what's the correct time now? Date: 11/10/2002 at 18:03:04 From: Doctor Ian Subject: Re: Watch gaining time Hi Ann, If the watch gains 6 minutes per hour, that's 360 seconds every 3600 seconds, or 1 second every 10 seconds. In other words, the clock is running 10% fast. We can use this to figure out what the actual time is from the displayed time. For example, suppose the watch reads 3:18. What's the actual time? Well, 3:18 is 3 hours + 18 minutes, which is 180 + 18 minutes, or 198 minutes. This must be the actual time, T, plus 10 percent, so T + T/10 = 198 (11/10)T = 198 T = 198 * (10/11) = 180 minutes or exactly 3:00. Can you take it from here? Try doing the same thing that I did, but instead of using 198 minutes, use the number of minutes from midnight to 8:26, instead of to 3:18. (You'll have to convert 8 hours and 26 minutes minutes to some total number of minutes.) - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ |
Search the Dr. Math Library: |
[Privacy Policy] [Terms of Use]
Ask Dr. Math^{TM}
© 1994-2015 The Math Forum
http://mathforum.org/dr.math/