Is the time in the clock 9 O’ clock now?
I. After half an hour, the minute and the hour hands of the clock will make an angle of exactly 90’C with each other.
II. Exactly 15 minutes back, the hour and the minute’s hand of the clock coincided with each other.

NOTE :- Angle between hour and minute hand in a clock = | 30 * H - $$\frac{11}{2}$$ * M| , where M -> minutes & H -> hour.

I : Lets assume time now is 9 o' clock. Then after half hour, time will be 9:30.

Angle between hour and minute hand at 9:30 = 30 * 9 - $$\frac{11}{2}$$ * 30 = 105

Since, angle formed is not 90. It contradicts our assumption.

$$\therefore$$ Ans - Time now is not 9 o' clock.

I alone is sufficient.

II : Lets assume time now is 9 o' clock. Then 15 minutes back, time will be 8:45

Angle between hour and minute hand at 8:45 = | 30 * 8 - $$\frac{11}{2}$$ * 45 | = |-7.5| = 7.5

Since, angle formed is not 0. It contradicts our assumption.

$$\therefore$$ Ans - Time now is not 9 o' clock.

II alone is sufficient.