Aptitude - Clock - Discussion

Past 9n means?

When asking will the hands of a watch be together?

Use (60/11)h.

= 60*9/11.
= 540/11.
= 49 1/11.

I don't understand the concept here you are assuming. In question from 9 to 10 o'clock the hands should be meet each other on 9.50 o'clock in real situation by watch.

But how could you say here they are meeting on 9.45 o'clock means we are suppose to assume hour hand at stable position?

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.

Can any one say how we can say that 49 1/11 = past 9?

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.

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.

I think it has gained 50 min space.

In Q6 at 7, they are 25 mins apart, but in this Q at 9 they are 45 mins apart, is the angle measured clockwise/ anti clockwise?

What to do when you take minute spaces in degrees instead of minutes?