Clocks(quantitative aptitude)
11 likes4,600 views
The document discusses concepts related to clocks, including: - Clock dials are divided into 12 hour spaces, with each hour space further divided into 5 minute spaces. - In 60 minutes, the minute hand gains 55 minutes on the hour hand. - Key points about the relationship between the hour and minute hands at different times, such as being coincident once per hour or at a 90 degree angle twice per hour. - A formula is provided to calculate the angle between the hands based on the number of hours and minutes.
![11. The inhabitants of planet Rahu measure
time in hours and minutes which are different
from the hours and minutes of our
earth. Their day consists of 36 hours with
each hour having 120 minutes. The dials of
their clocks show 36 hours. What is the angle
between the hour hand and the minutes hand
of a Rahuian clock when it shows a time of
9:48? [Rahuians measure angles in degrees
the way we do on earth. But for them, the
angle around a point is 720 degrees instead
of 360 degrees. ]](https://image.slidesharecdn.com/clocksquantitativeaptitude-160320103740/85/Clocks-quantitative-aptitude-27-320.jpg)
Clocks(quantitative aptitude)
- 2. Many of times questions appear on clocks in certain exams. here, we discuss some concept related to clocks covering all type of questions asked.
- 3. The dial of clock is a circle whose circumference is divided into 12 equal part, called hour space. Each hour space are further divided into 5 parts, called minute space . This way, the whole circumference is divided into 12*5 = 60 minute spaces.
- 4. The time taken by the hour hand (smaller hand) to cover a distance of an hour space is equal to the time taken by the minute hand (longer hand) to cover a distance of the whole circumference. Thus, we may conclude that in 60 minutes, the minute hand gains 55 minutes on the hour hand. Note : The above statement (underlined) is very much useful in solving the problems in this chapter, so it should be remembered. The above statement wants to say that :
- 5. “ In an hour, the hour-hand moves a distance of 5 minute spaces whereas the minute-hand a distance of 60 minute spaces. Thus the minute-hand remains 60 - 5 = 55 minute spaces ahead of the hour- hand.”
- 6. 1. In every hour, both the hands coincide once. 2. When the two hands are at right angle, they are 15 minute spaces apart. This happens twice in every hour. 3. When the hands are in opposite directions, they are 30 minute spaces apart. This happens once in every hour.
- 7. 4. The hands are in the same straight line when they are coincident or opposite to each other. 5. The hour hand moves around the whole circumference of clock once in 12 hours. So the minute hand is twelve times faster than hour hand. 6. The clock is divided into 60 equal minute divisions.
- 8. 7. 1 minute division = = = apart 8. The clock has 12 hours numbered from 1 to 12 serially arranged. 9. Each hour number evenly and equally separated by five minute divisions = (5× ) = apart.
- 9. 10. In one minute, the minute hand moves one minute division or . 11. In one minute, the hour hand moves 12. In one minute the minute hand gains more than hour hand.
- 10. 13. When the hands are together, they are apart. Hence, Formed in 12 hours Formed in 24 hours 11 22 22 44 θ
- 11. In a correct clock the hands of a clock coincide in every . If the hands of a clock coincide in less than then clocks gains time and if the hands of a clock coincide in more than then the clock looses time.
- 12. If a watch indicates 9.20, when the correct time is 9.10, it is said to be 10 minutes too fast. And if is said to be 10 minutes too fast. And if it indicates 9.00, when the correct time is 9.10, it is said to be 10 minutes too slow.
- 13. It is evident that the two hand of a clock will subtend an θ between them. At any time, the same can be found out using the following formula: here m= minutes and h= hours
- 27. 11. The inhabitants of planet Rahu measure time in hours and minutes which are different from the hours and minutes of our earth. Their day consists of 36 hours with each hour having 120 minutes. The dials of their clocks show 36 hours. What is the angle between the hour hand and the minutes hand of a Rahuian clock when it shows a time of 9:48? [Rahuians measure angles in degrees the way we do on earth. But for them, the angle around a point is 720 degrees instead of 360 degrees. ]