Aptitude - Clock - Discussion
Discussion Forum : Clock - General Questions (Q.No. 15)
15.
At what time between 9 and 10 o'clock will the hands of a watch be together?
Answer: Option
Explanation:
To be together between 9 and 10 o'clock, the minute hand has to gain 45 min. spaces.
55 min. spaces gained in 60 min.
| 45 min. spaces are gained in |  |
60 | x 45 |  min or 49 |
1 | min. |
| 55 | 11 |
 The hands are together at 49 |
1 | min. past 9. |
| 11 |
Discussion:
48 comments Page 2 of 5.
Babita dogra said:
9 years ago
How you take 55 mint? How it will come?
Explain it.!
Explain it.!
Rakha said:
9 years ago
What to do when you take minute spaces in degrees instead of minutes?
Harshitha said:
8 years ago
How come past 9 minutes? please explain it.
Ramya said:
10 years ago
I can't understand please explain it.
Nisha lakshmi said:
7 years ago
BTW 9 and 10 the hand of the clock will be together at 9:45(min and hr hand coincides).
Since 55 min gained by min hand in 60 min.
Thus 1 min gained by min hand in 60/55 min.
Now 45 min gained by min hand in 60/55 * 45 = 540/11 min.
Since 55 min gained by min hand in 60 min.
Thus 1 min gained by min hand in 60/55 min.
Now 45 min gained by min hand in 60/55 * 45 = 540/11 min.
Rohit@ said:
1 decade ago
I think it has gained 50 min space.
Sank said:
1 decade ago
We can solve this question as a speed - time question.
Initially at 9'o clock hour hand will be at 9 and minute hand will be at 12.
In 12 hour a hour hand gains angle = 360 degree.
So speed of hour hand will be 0.5 deg/min.
In 60 minutes a minute hand gains = 360 degree.
So speed of hour hand will be 6 deg/min.
Let after hour hand covers angle x both the hands coincide.
So angle covered by hour hand = x and by minute hand = 270+x.
x/0.5= (270+x)/6 (as time taken by both will be same).
x = 270/11.
As 1 min = 6 degrees, so we can convert above angle(x) in degree to minute.
So in minute it will be (270/11)/6 = 45/11.
So the time when both of the clock hands will coincide is 49 1/11.
Initially at 9'o clock hour hand will be at 9 and minute hand will be at 12.
In 12 hour a hour hand gains angle = 360 degree.
So speed of hour hand will be 0.5 deg/min.
In 60 minutes a minute hand gains = 360 degree.
So speed of hour hand will be 6 deg/min.
Let after hour hand covers angle x both the hands coincide.
So angle covered by hour hand = x and by minute hand = 270+x.
x/0.5= (270+x)/6 (as time taken by both will be same).
x = 270/11.
As 1 min = 6 degrees, so we can convert above angle(x) in degree to minute.
So in minute it will be (270/11)/6 = 45/11.
So the time when both of the clock hands will coincide is 49 1/11.
Laxmi said:
1 decade ago
Hello guys.
In previous question one member said that for angle formula.
Less 6 clock use formula theta = 11/2*M-(30*H).
And above 6 clock use formula theta = (30*H)-11/2*M.
This question this above 6.
But @Pradeep use formula is less 6.
I totally confused which one is correct formula in this question.
And when we use angle both the formulas. Any one please explain.
In previous question one member said that for angle formula.
Less 6 clock use formula theta = 11/2*M-(30*H).
And above 6 clock use formula theta = (30*H)-11/2*M.
This question this above 6.
But @Pradeep use formula is less 6.
I totally confused which one is correct formula in this question.
And when we use angle both the formulas. Any one please explain.
Sree said:
1 decade ago
Can any one say how we can say that 49 1/11 = past 9?
Rohan said:
1 decade ago
Let QH and QM be angular speed of hour and minute hand respectively.
QH = 360/720 = 0.5 (degree/minute) QM = 360/60 = 6 (degree/minute).
Relative angular speed (QM-QH) = 11/2 = 5.5.
Now at 9:45 angle between minute and hour hand will be = 22.5 deg.
Time taken for minute hand to coincide hour hand = 22.5/5.5 = 45/11.
= 45/11 = 4+1/11.
Hence time at which hour and minute hand coincide is:
Hour = 9 minute = 45+4+1/11 = 49+1/11 or 45 1/11 past 9.
QH = 360/720 = 0.5 (degree/minute) QM = 360/60 = 6 (degree/minute).
Relative angular speed (QM-QH) = 11/2 = 5.5.
Now at 9:45 angle between minute and hour hand will be = 22.5 deg.
Time taken for minute hand to coincide hour hand = 22.5/5.5 = 45/11.
= 45/11 = 4+1/11.
Hence time at which hour and minute hand coincide is:
Hour = 9 minute = 45+4+1/11 = 49+1/11 or 45 1/11 past 9.
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