My Math Forum how to solve this confusing clock problem?

 Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion

 October 11th, 2018, 09:42 PM #1 Senior Member   Joined: Aug 2014 From: India Posts: 343 Thanks: 1 how to solve this confusing clock problem? Q) At what time between 4-5, 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 12-position to be 0°, the minute hand will be at 0° and the hour hand will be at the 4-position = 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, 01:46 AM #2 Global Moderator   Joined: Dec 2006 Posts: 20,302 Thanks: 1974 30/5.5 = 60/11 Your friend also found the time when the minute hand is 90° beyond the hour hand.
October 12th, 2018, 04:33 AM   #3
Senior Member

Joined: Aug 2014
From: India

Posts: 343
Thanks: 1

Quote:
 Originally Posted by skipjack Your friend also found the time when the minute hand is 90° beyond the hour hand.
What is the meaning of "beyond the hour hand"?

 October 12th, 2018, 09:20 AM #4 Global Moderator   Joined: Dec 2006 Posts: 20,302 Thanks: 1974 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.
 October 18th, 2018, 12:23 AM #5 Member   Joined: Sep 2017 From: Saudi Arabia Posts: 37 Thanks: 1

 Tags clock, confusing, problem, solve

 Thread Tools Display Modes Linear Mode

 Similar Threads Thread Thread Starter Forum Replies Last Post Ganesh Ujwal Pre-Calculus 2 September 18th, 2018 01:35 AM Ganesh Ujwal Elementary Math 14 July 14th, 2018 03:08 AM Ganesh Ujwal Pre-Calculus 9 February 18th, 2018 05:14 AM Aman Verma Elementary Math 7 July 17th, 2014 10:23 AM Recipe Algebra 5 March 26th, 2010 02:20 PM

 Contact - Home - Forums - Cryptocurrency Forum - Top