Clock

A clock is a device that displays the time. It is circular and consists of three hands. The thin hand flickering every second is the second’s hand. The long and thick hand is the minute’s hand, and the shorthand is the hour’s hand. The movement of these hands in a clockwise direction gives us time. There are 12 numbers on the clock representing the time, and each number is divided by a time gap of 5 minutes.

Structure of the Clock 

The structure of the clock looks easy but is quite complicated indeed. The clock is circular and has three hands that keep moving along with time. Let’s learn some formulas regarding clocks – 

The total clock has 3600, divided into 12 numbers. The angle between any two consecutive numbers is obtained by dividing the 3600 by 12.

Example: Angle between 1 and 2 is 3600/12=300

Speed of the minute hand:

60 min= 3600

1 min=3600/600= 60

A minute needle covers the distance of one hour in 60 minutes, whereas an hour needle takes the same time to cover the distance of 5 minutes.

Questions on Clocks

There are many clock questions asked in the exams. There are, in general, three types of clock questions: angles based on clocks, a reflection of a clock, and faulty clocks.

Angle based on clocks

In this type of question, time is given, and we need to find the angle between the minute’s hand and the hour’s hand. To solve this type of problem, we need to know the angle of the clock, the angle of the minute hand, and the hour’s hand.

Tip: 

Hour’s hand: An hour’s hand takes 12 hours to complete one round.

(For 12hours clock) 12 hours= 360degree, 1 hour= 30degree and 1 minute= ½ degree

Minute’s hand: A minute’s hand takes 60 minutes to complete one round.

(For 12hours clock) 60 min= 360degree, 1 min= 6degree 

Second’s hand: A second’s hand takes 60 seconds to complete one round.

 (For 12hours clock) 60 sec= 360degree, 1 sec= 6degree 

Reflection of clock

In this type of question, the clock is supposed to be placed before or above a mirror or water surface. The time in the reflection image is given, and we need to find the exact time. To solve this type of question, we need to know how to calculate mirror images and estimate the correct time.

Tip:

If the given clock is 12 hours, then subtract the mirror image clock time by 11:60, and if it is 24-hour-clock, subtract it by 23:60.

For water images, if in the given time minutes <30, subtract from 18:30, and if minutes >30, subtract from 18:90. 

Faulty clock

In this type of question, a faulty or defective clock-based question is asked. If the correct time is 4 and the clock displays 4:10, it means the clock is gaining time. If it displays 3: 50, it means it is losing time.

Tip:  

Multiply the minutes with the time of gain/ loss. For gain, add to the real-time; for loss, subtract from the real-time.

Examples 

Let’s see a few examples along with a detailed explanation of obtaining the answers:

Question on angels 

The time displayed on a clock is 4 hrs 40 min, find the angle between hour and minute needle of the clock.

(A) 1000        (B) 800                    (C) 1200               (D) 2000

Answer:

1 hour = 300

So, 4 hours = 30 × 4 = 1200

1 min= ½ 0

40 min= 40 x ½ 0= 200

Now, the angle covered by both the needles = 1200 – 200 = 1000

Question on mirror image

A clock displaying only 3, 6, 9, 12 numbers is placed upside down in front of a mirror. The time in the reflection is 4.50, then what is the actual time?

(A) 08: 10 (B) 01: 40 (C) 04: 50 (D) 10: 20

Answer: The mirror image clock time is 4:50 means the hour’s hand is placed on the dot in the place of 4, and the minute’s hand is placed on the dot in the place of 11. But the mirror reverses the image.

So the hour’s hand is supposed to be on the dot opposite 11, i.e., 1, and the minute’s hand on the dot opposite 4,  i.e.,  8.

So the answer is 01:40

Question on Faulty clocks

A watch gains 5 seconds every 3 minutes. It was set right at 8 AM. What time will it show at 10 PM on the same day?

1. A) 10:25:02 B) 01:20:40 C) 10:23:20 D) 01:23:20

Answer: The watch gains 5 sec in 3 minutes, so in an, hour it gains 100 sec

The time difference between 8 AM and 10 PM on the same day = 

(12-8) + (12-4) = 4+10=14 hours

The time gained by 14 hours = 14 x 100= 1400 seconds

= 23 minutes 20seconds

When the time is 10 PM on the corrected watch, it would be 10 hours 23 minutes 20 seconds on the faulty clock.

Conclusion

The clocks are most important under the mental ability section in many competitive exams. They are the mark scorers and time savers. In this article, we have covered the key concepts of clocks, the types of questions asked on clocks, and solved the clock questions, formulas, and several tips. Clock questions are very tricky but easy to learn. To solve these questions easily and gain good scores, we need to develop observation, analysing, and critical thinking skills.