Aptitude - Clock - Discussion

At 5:30, the hands are 55 mins apart.To get an angle 90 btw them space must 15 mins apart,

so, the space is 55-15=40.
therefore,60/55-40=43 7/11.

At 5.30, Angle between hands is 15 degree and 75' more required to make a right angle. Relative angle made by hands is 11/2 ' in a minute.

We can assume in x min they cover remaining 75.
So 11/2 * x = 75.
x = 150/11 min.
So at 30 + 150/11 min, they make a right angle.

I didn"t understand this solution. Can anyone please explain?

How can you get 11/2 in the formula?

Can anyone help me? Please.

FORMULA :

Guess P = ANS .
(11/2) x (minutes) - 30 x (Hours) = 90 degree.
11/2 x P - 30 x 5 = 90,

P = 480/11= ANS.

Friends please help me, I don't know this chapter.

I was getting confused in using the formula.

But your answer helps me, Thankyou @Prashanth.

Since for 1 hour, the minute's arm move 360 degrees. And for each hour arm move 30 degrees.

Hence for every 1 degree move the minute's arm move 12 degrees.

When the time is 5 : 30 the angle between the min arm and hour arm is 15 degree.

Our target to find a time when the angle is 90 degree.

For this, we solve the equation :12x - x + 15 = 90.

From here we get x = 75/11.

30 degree = 1 hour.

75/11 degree = 1/30 * 75/11 = 5/22hours = 300/22min.

Hence final time is 30 + 300/22 = 480/22 min from 5 o'clock. (we add 30 because we have considered the arms move from 5:30).

Thanks @Harry.

Sorry @Riddilavan your formula may wrong if you solve this question.

How many minutes after 7 o'clock and before 8'o clock will the hands of the clock be in opposite direction?