MCQ
Time, speed and distance; time and work MCQ - Practice Questions with Answers
Solve 15 Time, speed and distance; time and work questions for RAS/RPSC preparation.
Practice questions
Q1A can complete a job in 12 days and B can complete the same job in 18 days. If they work together, how long will they take?
Treat the whole job as 1 or use the LCM method. The LCM of 12 and 18 is 36, so take total work as 36 units. A does 36/12 = 3 units per day and B does 36/18 = 2 units per day. Together they do 5 units per day. Time required is total work divided by combined daily work: 36/5 = 7.2 days. This also avoids the common trap of adding 12 and 18.
Q2A boat has a downstream speed of 18 km/h and an upstream speed of 12 km/h. Which pair correctly gives its still-water speed and stream speed?
For boats and streams, downstream speed equals still-water speed plus stream speed, and upstream speed equals still-water speed minus stream speed. Therefore, still-water speed is the average of the two observed speeds: (18 + 12)/2 = 15 km/h. Stream speed is half of their difference: (18 - 12)/2 = 3 km/h. The calculation also checks logically because downstream becomes 15 + 3 = 18 and upstream becomes 15 - 3 = 12.
Q3Which statement is incorrect for CET-level time, speed, distance and work-rate questions?
For a partly filled tank, the whole tank is still the complete unit, but the remaining work is only the unfilled part. If a tank is half-filled already, the work left is 1/2 tank, not 1 full tank. The other statements follow directly from the study note: 72 km/h becomes 20 m/s by multiplying by 5/18, a train crossing a pole clears its own length, and time is distance divided by speed.
Q4Match the situation with the correct rule. I. Two runners move on a circular track in the same direction. II. Two vehicles move towards each other. III. A train crosses a platform. IV. A filling pipe and a leakage pipe are both open.
Same-direction circular-track questions use the difference of speeds because the faster runner gains only by the extra speed. Vehicles moving towards each other use the sum of speeds because the gap closes from both sides. A train crossing a platform must cover train length plus platform length, not just one of them. In pipe questions, filling is positive and leakage or emptying is negative, so the net rate is filling rate minus leakage rate.
Q5A boat moves at 12 km/h in still water, and the stream speed is 3 km/h. How much time will it take to travel 45 km downstream?
Downstream means the stream helps the boat, so the effective speed is still-water speed plus stream speed. Here downstream speed = 12 + 3 = 15 km/h. Time is distance divided by speed, so time = 45/15 = 3 hours. Subtracting 3 would create the upstream speed of 9 km/h and give a different journey time. Using only 12 km/h also ignores the relative-speed idea.
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More questions
6A train 150 m long crosses a pole in 10 seconds. What is its speed in km/h?
7Which statement is incorrect for the rules in time-speed-distance and work-rate questions?
8Match each problem situation with the correct working idea. List I 1. A and B complete a job in 12 and 18 days 2. Tank is already half-filled 3. Same-direction circular runners 4. Equal time at 20 km/h and 40 km/h List II P. Use the simple average of speeds Q. Remaining work is 1/2 tank R. Add work rates 1/12 and 1/18 S. Use track length divided by speed difference
9Two cyclists move towards each other at 12 km/h and 18 km/h. They are 15 km apart. What is the time taken to meet?
10Assertion: If A finishes a job in 12 days and works alone for 3 days, A completes 1/4 of the job. Reason: In work questions, work done in a given time is rate multiplied by time.
11A bus moves at 54 km/h for 40 seconds. If units are handled correctly, what distance does it cover?
12A completes a job in 10 days and B completes the same job in 15 days. Working together, how many days will they take?
13Assertion: If a person travels for 1 hour at 20 km/h and for 1 hour at 40 km/h, the average speed is 30 km/h. Reason: For equal time intervals, average speed is the simple average of the speeds.
14A car travels 60 km at 30 km/h and returns 60 km at 60 km/h. Which value is the average speed for the whole journey?
15Which statement about train-crossing questions is correct?