
Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion 
 LinkBack  Thread Tools  Display Modes 
October 11th, 2018, 08:42 PM  #1 
Senior Member Joined: Aug 2014 From: India Posts: 331 Thanks: 1  how to solve this confusing clock problem?
Q) At what time between 45, both hands of clock right angle side. A) The minute hand moves 1/60th of the way around every minute. So it moves 6° per minute. The hour hand moves 1/12th = 30° every hour. So it moves 0.5° every minute. At 4 o'clock, taking the 12position to be 0°, the minute hand will be at 0° and the hour hand will be at the 4position = 120°. After n minutes, the minute hand will be at (0+6n)° = (6n)° and the hour hand will be at (120+0.5n)°. We want the difference to be 90°, so; 120 + 0.5n  6n = 90 30 = 5.5n n = 5.454545 So the time will be 4:05:27 My friend got two answers: 4h60/11 min and 4h420/11 min. I am confused. 
October 12th, 2018, 12:46 AM  #2 
Global Moderator Joined: Dec 2006 Posts: 19,700 Thanks: 1804 
30/5.5 = 60/11 Your friend also found the time when the minute hand is 90° beyond the hour hand. 
October 12th, 2018, 03:33 AM  #3 
Senior Member Joined: Aug 2014 From: India Posts: 331 Thanks: 1  
October 12th, 2018, 08:20 AM  #4 
Global Moderator Joined: Dec 2006 Posts: 19,700 Thanks: 1804 
As the minute hand is moving much faster than the hour hand, it will overtake it and reach an angle of 90 degrees with it before 5 o’clock.


Tags 
clock, confusing, problem, solve 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
How to solve this confusing Simple interest problem?  Ganesh Ujwal  PreCalculus  2  September 18th, 2018 12:35 AM 
How to solve this confusing question?  Ganesh Ujwal  Elementary Math  14  July 14th, 2018 02:08 AM 
How to solve this problem regarding clock strikes?  Ganesh Ujwal  PreCalculus  9  February 18th, 2018 04:14 AM 
Clock Problem  Aman Verma  Elementary Math  7  July 17th, 2014 09:23 AM 
Clock Problem  Recipe  Algebra  5  March 26th, 2010 01:20 PM 