A Train Travelling at a Certain Constant Speed takes 30 seconds GMAT Problem Solving

Question: A train travelling at a certain constant speed takes 30 seconds longer to travel 2 kilometers than it would take to travel 4 kilometers at 120 kilometers per hour. At what speed, in kilometers per hour, is the train travelling?

1. 24
2. 40
3. 48
4. 96
5. 120

“A train travelling at a certain constant speed takes 30 seconds longer to travel 2 kilometers than it would take to travel 4 kilometers at 120 kilometers per hour. ”– is a topic of the GMAT Quantitative reasoning section of GMAT. This question has been taken from the book “GMAT Quantitative Review”. To solve GMAT Problem Solving questions a student must have knowledge about a good amount of qualitative skills. The GMAT Quant topic in the problem-solving part requires calculative mathematical problems that should be solved with proper mathematical knowledge.0

Answer

As we know that to calculate the time taken, we will use the formula:

\(time=\frac{distance}{rate}\)

Time to travel 4 kilometers at 120 kilometers per hour is:

Given values:

distance travelled = 4 kilometers

rate = 120 kilometers per hours

\(time=\frac{distance}{rate}=\frac{4}{120}hours \)

Convert the given value in seconds, we will get:

\(time=\frac{4*3600}{12}seconds \)= 120 seconds

Time to travel 2 kilometers at regular speed: 120 + 30 = 150 seconds.

Now, we will convert 150 seconds to hours, we will get:

\(=\frac{150}{3600}hours =\frac{1}{24}hours \)

So, the speed of the train is calculated as:

\(rate=\frac{distance}{time}\) = \(\frac{2}{\frac {1} {24}}\) = 48 kilometers per hour

Correct option: C

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