Answer

Verified

439.2k+ views

**Hint**: In this particular question use the concept of speed, distance and time which is related as, $ {\text{speed}} = \dfrac{{{\text{distance}}}}{{{\text{time}}}} $ , and assume any variable be the length of the platform in meters and use the concept that in 1 km there is 1000 m and in 1 hour there is 60 minutes so use these concepts to reach the solution of the question.

**:**

__Complete step-by-step answer__Given data:

Length of the train, L = 130 m

Crosses a platform in 30 sec, with a speed of 45Km/hr.

Let, t = 30 sec.

And, v = 45 km/hr.

As we know that 1 km = 1000 m and 1 hr. = 60 min = 3600 sec.

So 45 km/hr. = $ \dfrac{{45\left( {1000} \right)}}{{3600}} = \dfrac{{450}}{{36}} = \dfrac{{25}}{2} $ m/s.

Therefore, v = $ \dfrac{{25}}{2} $ m/s.

Now as we know that speed, distance and time is related as, $ {\text{speed}} = \dfrac{{{\text{distance}}}}{{{\text{time}}}} $

$ \Rightarrow v = \dfrac{D}{t} $ ............. (1)

Let the length of the platform be L’ meters.

So the total distance (D) train has to be covered in 30 sec = L + L’ = 130 + L’ meters.

$ \Rightarrow D = 130 + L' $

Now substitute the values in equation (1) we have

$ \Rightarrow \dfrac{{25}}{2} = \dfrac{{130 + L'}}{{30}} $

Now simplify it we have,

$ \Rightarrow \dfrac{{25}}{2}\left( {30} \right) = 130 + L' $

$ \Rightarrow L' = \dfrac{{25}}{2}\left( {30} \right) - 130 = 375 - 130 = 245 $ Meters.

So this is the required length of the platform.

**Note**: Whenever we face such types of questions the key concept we have to remember is that as the units of speed is given is km/hr. unit of time is in sec and unit of length of train in meters so if we directly substitute these values into the formula then there is a mismatch in the units, so first we have to change the unit of speed to m/s from km/hr. as above then substitute these values in the formula and simplify as above we will get the required answer, always remember that the total distance covered by the train is the sum of length of the platform and the length of the train.

Recently Updated Pages

Mark and label the given geoinformation on the outline class 11 social science CBSE

When people say No pun intended what does that mea class 8 english CBSE

Name the states which share their boundary with Indias class 9 social science CBSE

Give an account of the Northern Plains of India class 9 social science CBSE

Change the following sentences into negative and interrogative class 10 english CBSE

Advantages and disadvantages of science

Trending doubts

Which are the Top 10 Largest Countries of the World?

Difference between Prokaryotic cell and Eukaryotic class 11 biology CBSE

Fill the blanks with the suitable prepositions 1 The class 9 english CBSE

Differentiate between homogeneous and heterogeneous class 12 chemistry CBSE

How do you graph the function fx 4x class 9 maths CBSE

Select the word that is correctly spelled a Twelveth class 10 english CBSE

The Equation xxx + 2 is Satisfied when x is Equal to Class 10 Maths

Give 10 examples for herbs , shrubs , climbers , creepers

Change the following sentences into negative and interrogative class 10 english CBSE