Question

At what time between 70' clock and 8 o'clock will the two hands of a clock be at right angles?

21 9/11 minutes past 7
54 6/11 minutes past 7
Both (1) and (2)
None of these
​

Answer 1

Answer:

There are two cases

Case I : When they are in opposite directions i.e. 30 min spaces apart

At 8 o'clock they are 40 minute spaces apart

To be in opposite directions minute hand will have to gain 40 - 30 = 10 min spaces

Now 10 minute spaces will be gained in

6055×10=1010116055×10=101011 minute

Hence hand will be in opposite