Question

Every floor of a 25 storey building is 5m high. If a lift moves 2 meters every second, how long will it take to move from 3rd floor to 15th floor?
A.32 seconds
B.42 seconds
C.30 seconds
D.25 seconds

Answer 1

Hint: The most important formula that would be used in this question is the relation between the distance, speed and the time that is passed which is as follows
\[distance=speed\times time\]

Complete step-by-step answer:
Firstly, we will try to find the total distance that is to be travelled by the lift that is the height difference between the 3rd and the 15th floor.
As the speed of the lift is also given, we can easily calculate the time that the lift will take to cover the difference in height.


As mentioned in the question, we have to find the time that will be required by the lift to reach the 15th floor from the 3rd floor.
As mentioned in the hint, we know that each floor has a height of 5m. Now, the height or the distance between the floors can be calculated as follows
\[distance=(15-3)\times 5=60m\]
Now, the lift’s speed is given as 2m/sec, hence, we can know the time required as follows
Using the formula given in the hint, we can find the time as follows
\[\begin{align}
  & 60=2\times time \\
 & time=\dfrac{60}{2} \\
 & time=30\sec \\
\end{align}\]
Hence, the time required is 30sec.

Note:-The students can make an error if they don’t know the formula or the relation between the distance, time and the speed that is mentioned in the hint as follows
\[distance=speed\times time\]
The students can also make an error in calculating the height difference between the 3rd and the 15th floor.