Machine-translated by Google. Questions are authored in English.
Top

Clocks Questions and Answers

Important Instructions
111.

At what angle the hands of a clock are inclined at 15 minutes past 5?

Answer: B

The hour hand moves \( 0.5^{\circ} \) a minute and the minute hand \( 6^{\circ} \), so at \( H \) hours \( M \) minutes the angle between them is

\[ \theta = \left| 30H - 5.5M \right| \]

\[ \theta = \left| 30(5) - 5.5(15) \right| = \left| 150 - 82.5 \right| \]

\[ = 67.5^{\circ} \]

The minute hand sits on the 3 and the hour hand a quarter of the way past the 5, so the gap is a little under the \( 60^{\circ} \) between the 3 and the 5.

Please log in or register to report this question.

112.

Find at what time between 8 and 9 o'clock will the hands of a clock be in the same straight line but not together ?

Answer: B

The hour hand moves \( 0.5^{\circ} \) a minute and the minute hand \( 6^{\circ} \), so at \( H \) hours \( M \) minutes the angle between them is

\[ \theta = \left| 30H - 5.5M \right| \]

\[ \left| 240 - 5.5M \right| = 180 \]

\[ 5.5M = 60 \quad\Longrightarrow\quad M = \frac{120}{11} \]

That is \( 10\tfrac{10}{11} \) minutes past 8. The other root, \( 5.5M = 420 \), gives \( M = 76.4 \), beyond the hour.

Please log in or register to report this question.

113.

The reflex angle between the hands of a clock at 10.25 is

Answer: A

The hour hand moves \( 0.5^{\circ} \) a minute and the minute hand \( 6^{\circ} \), so at \( H \) hours \( M \) minutes the angle between them is

\[ \theta = \left| 30H - 5.5M \right| \]

\[ \theta = \left| 300 - 137.5 \right| = 162.5^{\circ} \]

The reflex angle is what is left of the full turn:

\[ 360 - 162.5 = 197.5^{\circ} = 197\tfrac{1}{2}^{\circ} \]

A reflex angle is by definition greater than \( 180^{\circ} \), so the smaller 162.5 cannot be the answer.

Please log in or register to report this question.

114.

The angle between the minute hand and the hour hand of a clock when the time is 8:30  

Answer: B

The hour hand moves \( 0.5^{\circ} \) a minute and the minute hand \( 6^{\circ} \), so at \( H \) hours \( M \) minutes the angle between them is

\[ \theta = \left| 30H - 5.5M \right| \]

\[ \theta = \left| 30(8) - 5.5(30) \right| = \left| 240 - 165 \right| = 75^{\circ} \]

At half past the hour the hour hand has moved \( 15^{\circ} \) beyond the 8, which is why the answer is not the round \( 90^{\circ} \) between the 6 and the 8.

Please log in or register to report this question.

115.

How much does a watch lose per day, if its hands coincide ever 64 minutes?

Answer: A

In a correct clock the hands coincide every

\[ \frac{720}{11} = 65\tfrac{5}{11} \text{ minutes} \]

Here they take 64 minutes, less than they should, so the watch is running fast - but the question asks how much it loses, and the conventional treatment measures the shortfall of the interval:

\[ \frac{720}{11} - 64 = \frac{16}{11} \text{ minutes per interval} \]

\[ \frac{16}{11} \times \frac{1440}{64} = \frac{23040}{704} = 32\tfrac{8}{11} \text{ minutes a day} \]

The 24-hour figure comes from the number of coincidence intervals in a day, \( \tfrac{1440}{64} = 22.5 \).

Please log in or register to report this question.

Loading…
Tags: Clocks Questions and Answers || Clocks MCQ Questions and Answers || Clocks GK Questions and Answers || Clocks GK MCQ Questions || Clocks Multiple Choice Questions and Answers || Clocks GK || GK on Clocks || Quantitative Aptitude Questions and Answers || Quantitative Aptitude MCQ Questions and Answers || Quantitative Aptitude GK Questions and Answers || GK on Quantitative Aptitude