At what approximate time between 4 and 5 am will the hands of a clock be at right angle? Choose the correct choice from the following
A) 4 : 40 am B) 4 : 38 am C) 4 : 35 am D) 4 : 39 am E) None of these
Here H × 30 = 4 × 30 = 120°.   (Since initially the hour hand is at 4. ∴ H = 4).   Required angle A = 90° and since, H × 30 &gt; A° so, there will be two timings.   Required time T = 2⁄11(H × 30 ± A) minutes past H.   ∴ One timing = 2⁄11(4 × 30 + 90) minutes past 4   = 382⁄11 minutes past 4.   Or 4 : 38 approx.   Answer 4 : 38 am
<result>B</result>
At what approximate time between 4 and 5 am will the hands of a clock be at right angle?