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At what time between 5 : 30 and 6 O'Clock, will the hands of a clock be at right angle ?

Solution

Correct Option: 3

At 5:00, hour hand is at 150 degrees. For a right angle (90 degrees apart), the minute hand should be at 150+90=240150 + 90 = 240 degrees from 12. Minute hand position at mm minutes past 5 is 6m6m degrees. Setting up: minute hand gains 5.5 degrees per minute on hour hand. At 5:00 they are 150 degrees apart. Need 90 degrees: 1505.5m=90150 - 5.5m = 90, so m=605.5=12011=101011m = \frac{60}{5.5} = \frac{120}{11} = 10\frac{10}{11} (before 5:30, not in range). For 90 degrees with minute ahead: 5.5m150=905.5m - 150 = 90, m=2405.5=48011=43711m = \frac{240}{5.5} = \frac{480}{11} = 43\frac{7}{11}.

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