Aptitude - Clock - Discussion

We can do this question very simply by using following formula..

360-(30H- 11/2M ).

Where H = 10 and M= 25.. easy na ?

We can use this formula too,
Reflex angle = 360-theta.
Theta = 1/2(60h-11m).

We have formula also angle = |(11/2)*min-(30*hour)|.

But, @Karthik, using the formula that you have mentioned, I got wrong answer.

Formula for cal angle = 11/2*mins-30*hrs.

Therefore 11/2*25-30*10 = 137.5-300 = 163.5.

Reflex angle = 360-163.5 = 197.5 answer.

The formula is wrong. The correct formula is:

The angle between the hands of the clock = (60xH - 11xM)/2.

But in the above question, according to formula (60Xh-11Xm)/2.

(60X10-11X25)/2.

(600-275)/2.

375/2.

= 162.5.

Reflex angle = 360-162.5 = 197.5.

So, simple when the question asks between 1-11.

Take a formula as 11:60 - Time.

11:60 - 10:25 = 1:35 is the answer.

10:25 = 10 hrs + 25 min. Therefore, total angle between them.

[angle at 10 hrs (=60 deg) + angle during 25 min movement (=150(min needle)-12.5(hrs needle) = 137.5 deg)]

= 60 + 137.5 = 197.5 or 197(1/2) degree.

Refer explanation below:

At 10 hrs, angle between them = 60 degree.

During 25 min movement both needle will move. At 25 min minute needle will make an angle = 25 x 30 = 150 degree.

Simultaneously, hrs needle also will move an angle = 12.5 degree. (as hrs needle make 360 degree in 12 hrs or 720 min. Therefore, in 25 min, angle = 25x360/720 = 12.5 degree.).

There is no easy way to understand in spite of this explanation.

I want clear definition of reflex angle and formula.