Quantitative Aptitude · Counting, Probability, Calendar & Clocks
Clocks — Questions & Answers
The minute hand moves 6° per minute, the hour hand 0.5° per minute, so the minute hand gains 5.5° on the hour hand each minute. Most clock questions are one application of that gain.
- 5 solved questions
- Step-by-step AI walkthroughs
- Key formulas included
Key formulas
Angle of hour hand from 12: 30H+0.5M degrees; minute hand: 6M degrees
Angle between hands =∣30H−5.5M∣ degrees (take 360− that if it exceeds 180)
The hands coincide every 65115 minutes
5 solved Clocks questions
What is the angle between the hands of a clock at 3:00?
Solution — answer C
At 3:00 the minute hand is at 12 and the hour hand at 3, three hour-marks apart: 3×30∘=90∘.
4 steps · reveal one at a timeStep 1: Hand Positions
First, let's identify where the hands are at 3:00. The minute hand will be pointing straight up at the 12. The hour hand will be pointing directly at the 3.
Step 2: Angle per Mark
A full circle on a clock face is 360∘. There are 12 hour marks around the clock. This means the angle between any two consecutive hour marks is 360∘/12=30∘.
Step 3: Calculate Total Angle
At 3:00, the minute hand is at 12 and the hour hand is at 3. These positions are 3 hour marks apart (from 12 to 1, 1 to 2, and 2 to 3). So, the total angle is 3×30∘=90∘.
Step 4: The answer
So the answer is (C) 90°. The hands of a clock at 3:00 form a right angle, which is 90∘.
How many degrees does the minute hand of a clock move in 20 minutes?
Solution — answer B
The minute hand moves 6∘ per minute, so in 20 minutes it moves 6×20=120∘.
4 steps · reveal one at a timeStep 1: Clock face basics
A clock face is a circle, which means it covers 360∘. The minute hand completes one full rotation around the clock in 60 minutes.
Step 2: Minute hand speed
To find out how many degrees the minute hand moves per minute, we divide the total degrees by the total minutes: 360∘÷60 minutes. This gives us 6∘ per minute.
Step 3: Calculate total movement
Now we know the minute hand moves 6∘ every minute. We need to find out how much it moves in 20 minutes. We multiply the degrees per minute by the number of minutes: 6∘×20 minutes.
Step 4: The answer
So the answer is (B) 120°. The minute hand moves 6∘ per minute, so in 20 minutes it moves 6×20=120∘.
What is the angle between the hands of a clock at 4:20?
Solution — answer D
Hour hand =30(4)+0.5(20)=130∘; minute hand =6(20)=120∘. The angle between them is 130−120=10∘.
3 steps · reveal one at a timeStep 1: Calculate Hour Hand
First, let's find the angle of the hour hand from the 12 o'clock mark. The hour hand moves 30∘ per hour and 0.5∘ per minute. At 4:20, its angle is 30(4)+0.5(20)=120+10=130∘.
Step 2: Calculate Minute Hand
Now, let's find the angle of the minute hand from the 12 o'clock mark. The minute hand moves 6∘ per minute. At 20 minutes past the hour, its angle is 6(20)=120∘.
Step 3: The answer
So the answer is (D) 10°. The angle between the hands is the absolute difference between their positions: 130∘−120∘=10∘.
At what time between 2 and 3 o'clock do the hands of a clock coincide?
Solution — answer C
At 2:00 the hour hand leads the minute hand by 60∘. The minute hand gains 5.5∘ per minute, so it closes the gap in 5.560=11120=101110 minutes past 2.
4 steps · reveal one at a timeStep 1: Initial hand positions
First, let's find the positions of the hands at 2 o'clock. The minute hand points at 12, which is 0∘. The hour hand points at 2. Since each hour mark is 30∘, the hour hand is at 2×30∘=60∘. The hour hand leads by 60∘.
Step 2: Relative speed
Next, we find how fast the minute hand gains on the hour hand. The minute hand moves 6∘ per minute, and the hour hand moves 0.5∘ per minute. So, the minute hand gains 6∘−0.5∘=5.5∘ on the hour hand every minute.
Step 3: Time to coincide
To coincide, the minute hand must cover the initial 60∘ lead of the hour hand. Using the relative speed, the time taken is distance/speed=60∘/5.5∘ per minute. This simplifies to 60/(11/2)=120/11 minutes.
Step 4: The answer
So the answer is (C) 2:10 1110. The time is 120/11 minutes past 2 o'clock, which is 101110 minutes past 2.
A clock gains 5 minutes every hour. If it is set right at 12 noon, what time will it show when the correct time is 6 p.m. the same day?
Solution — answer B
In the 6 hours from noon to 6 p.m. the clock gains 5×6=30 minutes, so it shows 6:30 p.m.
3 steps · reveal one at a timeStep 1: Calculate total time
The clock is set correctly at 12 noon. We need to find out what time it shows when the correct time is 6 p.m. This means a total of 6 hours have passed.
Step 2: Find total gain
The problem states the clock gains 5 minutes every hour. Since 6 hours have passed, the total time gained by the faulty clock will be 5×6=30 minutes.
Step 3: The answer
So the answer is (B) 6:30 p.m. The clock will show the correct time of 6 p.m. plus the 30 minutes it gained, resulting in 6:30 p.m.
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