Clock Problem with Strong Fundamental concepts Tricks, and Shortcuts for Competitive Exams like cds, nda ibps, ssc, railway, govt job , police,defence, ias, oas , ossc, mba, mca …
Clock Problem Question Answer Fundamental concepts Tricks and Shortcuts for Competitive Exams like ibps, cds, nda, ssc, railway, govt job , police, defense, ias, oas
INTRODUCTION
A clock is an important material in our daily life. We can not think a single day without it. We use a clock to measure the time. A clock is a device used to tell time. A clock may be analog or digital. Parts of a Clock / Watch (analog)
◘ Crystal- a piece of glass / plastic that
protects the face of a clock / watch
◘ Dial- the part of a clock / watch
that is round and has hands
that move to show you the time
◘ Face- the front of a clock,
where the numbers are
◘ Hand- the hands on a clock
are the long parts that move
round and show the time.
The minute hand (MH) is also called
the long hand (points to the minute) and
the hour hand (HH), the short hand (points to the hour) and the
thing that points to the seconds is called the second hand.
The face of a clock or a watch is a circle which is divide d to 60 minute spaces. The minutes hand passes over 60-minute spaces while the hours hand goes over 5-minute spaces. That is, in 60 minutes the minutes hand gains 55 inutes on the hour hand.
A clock is a complete circle having 360 degrees. It is divided into 12 equal parts i.e. each part is 360/12 = 30°. As the minute hand takes a complete round in one hour, it covers 360° in 60 minutes.
In 1 minute it covers 360/60 = 6°/ minute.
Also, as the hour hand covers just one part out of the given 12 parts in one hour. This implies it covers 30° in 60 minutes i.e. ½° per minute.
This implies, the relative speed of the MH is 6–½= 5 ½ °/ minute.
We will use the concept of relative speed and relative distance while solving problems on clocks.
In every hour
(i) The hands coincide once.
(ii) They are twice at right angles when the hands are 15 minutes
spaces apart.
(-1-)
(iii) They point in the opposite directions once when they are 30
minutes spaces apart.
(iv) The hands are in the same straight line when they are
coincident or opposite to each other.
→Too fast -If a clock indicates 9 : 20 when the correct time is
9:00, it is said to be 20 min too fast.
→Too slow — If it indicates 7 : 50, when the correct time is 8 : 00,
it is said to be 10 min slow.
Points to Remember
● Unless otherwise mentioned all the Angles are measured
from North direction; In clock wise direction.
● The hands of a clock coincide 11 times in every 12 h (Since
between 11 and 1, the coincide only once, i.e 12 o’clock).
→The hands coincide 22 times in a day.
● The hands of a clock point in opposite directions (in the
same straight line) 11 times in every 12 hours (Because
between 5 and 7 they point in opposite directions at 6 o’
clock only). So, in a day, the hands point in the opposite
directions 22 times
● In 12 hours, the hands coincide or in opposite direction 22 times.
In a day,the hands coincide or are in opposite direction 44 times.
● In 12 hours, they are at right angles 22 times.(The two hands for
right angles twice every hour. But the hands are at right angles
only once between 2 and 3 o’clock, & between 8 and 9 o’clock.) → In 24 hours, they are at right angles 44 times.
● Hands of the clock interchange positions after every 55
min.
Types of questions:
Usually, three types of questions are asked from this topic:
1. Finding the time when the angle between the 2 hands is given.
2. Finding the angle between the 2 hands at a given time.
3. Questions on clocks gaining / losing time.
(-2-) www.theplanetvidya.org
Planet Vidya, HO: Behind SBI ATM, Acharya Vihar Colony (9853355402) Planet Vidya, HO: Behind SBI ATM, Acharya Vihar Colony (9437081288)
Problems on Clock
II EXERCISES II
1. An accurate clock shows 7 : 15 a.m. , through how may degrees will the hour hand rotate when the clock shows 2 : 45 p.m.?
1) 144° 2) 150° 3) 225° 4) 168° 5) None of these
2. How many times in a day, the hands of a clock are straight?
1) 22 2) 24 3) 44 4) 48 5) None of these
3. It is between 4 P.M. and 5 P.M. and the angle between the hour and the minute hand of clock is 10°. What time does the clock show?
1) 4.10 pm 2) 4.15 pm 3) 4.20 pm 4) 4.25 pm 5) 4.15 pm
4. It is between 1 A.M. and 2 A.M. and the angle between the hour and the minute hand of clock is 135°. What time does the clock show?
1) 1.25 am 2) 1.30 am 3) 1.35 am 4) 1.40 am 5) 1.45 am
5. At what angle will the pointers be inclined at 2hr 15 min?
1) 200° 2) 207° 3) 209° 4) 215° 5) None of these
6. The angle between the minute hand and the hand of a clock when the time is 5.30, is
1) 11° 2) 13° 3) 15° 4) 18° 5) 20°
7. If a clock strikes six in 30 seconds, then it will strike 12 in how many seconds?
1) 50 sec 2) 60 sec 3) 65 sec 4) 66 sec 5) 69 sec
8. At what time between 5 and 6 O’ clock are the hands of a clock 3 minute spaces apart?
1) 10min 2) 12min 3) 13min 4) 14min 5) 24min
9. A watch gains 10 seconds in 6 minutes and was set right at 9 AM. What time will it show at 11 PM on the same day ?
1) 11 : 27 : 41 AM 2) 9: 51 : 04 AM 3) 10 : 45 : 15 PM 4) 11 : 23 : 20 PM 5) 11 : 20 : 23 PM
10. A watch which gains 10 seconds in 6 minutes was set right at 9 a.m. In the afternoon of the same day, when the watch indicated quarter past 6 o’clock, the true time is:
1) 6pm 2) 7pm 3) 8pm 4) 9pm 5) 11pm
11. A clock is set right at 6 a.m. The clock loses 16 minutes in a day. What will be the true time when the clock indicates 11 p.m. on 4th day?
1) 11am 2) 12am 3) 1am 4) 2am 4) 3am
12. A Wall Clock loses 10 minutes in every 2 hours and was set right at 7am on a Sunday. When will it show the correct time again?
1) 10AM on Sunday 2) 9AM on Sunday
3) 7AM on Saturday 4) 9AM Saturday 5) 8AM on Saturday
13. Suppose a Table Clock was correct at midnight, but then it began to lose 15 minutes each hour. It now shows 6 a.m. but it stopped 5 hours ago. What is the correct time now?
1) 9.30 a.m. 2) 11 a.m. 3) 11.30 a.m 4) 1 p.m 5) 1.30 p.m.
14. A watch gains uniformly, It was 3 min slow at 7 am on Monday the 3rd May, and fast by 5 min 36sec on May 12th 6 am. When was it correct?
1) 7am 10th May 2) 8 pm 8th May 3) 10am 6th May
4) 4pm 6th May 5) 9am 7th May
15. Two clocks are set to show 10am on Monday. One clock will run 4 minutes faster in a day. The other clock will run 4 minutes slower in every 36 hours. When will both the clocks show the same time again?
1) 12:30 at night, after 100 days 2) 12 noon, after 855 days
3) 1:30 am after 120days 4) 12 am after 105days
5) 10am after 108 days www.theplanetvidya.org
16. It was between 3 and 4 o’clock; but I, mistaking the hour hand for the minute hand thought that it was 55 min later the correct time. The correct time was
1) 12 minutes past 3 2) 24 minutes past 3
3) 36 minutes past 3 4) 48 minutes past 3 5) None of these
Planet Vidya, HO: Behind SBI ATM, Acharya Vihar Colony (9853355402) Planet Vidya, HO: Behind SBI ATM, Acharya Vihar Colony (9437081288)
ANSWER
1) 225 2) 44 3) 4.20 pm 4) 1.30 am 5) 215° 6) 15° 7) 66 sec 8) 24min 9) 4) 11 : 23 : 20 PM 10) 6pm 11) 12pm 89 hrs 12) 7AM on Saturday 13) 1 p.m. 14) 9am 6th May 15) 5) 10am after 108 days 16) 17) 18) 19) 20)
