Clocks foundation

Concept name:– Clocks

Concept explanation:   In one hour minute hand travel 360 degrees and Hour hand travel 30 degrees.

Sample set: Read the information given below and answer the questions that follow:

Q) At what times between 4’0 Clock and 5’0 Clock, will the hour hand and minute hand be 87 degrees apart from each other for the first time?

Ans. At 4’0 Clock, the minute and hour hand are 120 degrees apart. Now, the Relative speed between both hands = 330 degrees/hr. They need to travel relatively 33 degrees so that angle becomes 87 degrees.

Time =  (33/330)hrs =  (1/10) hr = (1/10) * 60 mins = 6 mins

So time will be 4:06

Level of difficulty: Easy

Q) How many times a day does minute hand meet the hour hand?

Ans: Let's start with 12 am. Both hands are together. When will they meet again? When the minute hand travels 1 circle relative to the hour hand. So time to meet = 1 circle/ relative speed of the clock hands. So, time taken would be 360 degrees/5.5 degrees per minute = 720/11 minutes.

So, how many times will this happen in 24 hours?

= 24*60/(720/11) = 2*11 = 22 times

Level of difficulty: Easy

Happy learning!

Rahul Sir

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