Question

A car covers 72 km in 2 hours and a train covers 120 km in 3 hours. Find the ratio of their speed. ​

Answer 1

$speed \: of \: car = \frac{72km}{2h} \\ = 36km {h}^{ - 1} \\ speed \: of \: train = \frac{120km}{3h} \\ = 40km {h}^{ - 1} \\ = \frac{speed \: of \: car}{speed \: of \: train} \\ = \frac{36km {h}^{ - 1} }{40km {h}^{ - 1} } \\ = \frac{36}{40} \\ = \frac{9}{10}$

Answer 2

Given :

• A car covers 72 km in 2 hours.
• A train covers 120 km in 3 hours.

To Find :

Ratio of their speeds.

Solution :

Analysis :

Here we first have to find the speed of both the car and the train. Then we have to reduce the speed of the car and the train in its simplest form. Then will get our ratio.

Required Formula :

Speed = Distance/Time

Units :

• Distance = km
• Time = hour
• Speed = km/hr

Explanation :

Speed of car :

We know that if we are given the distance and time of a moving object and is asked to find the speed then our required formula is,

Speed = Distance/Time

where,

• Distance = 72 km
• Time = 2 hrs

Using the required formula and substituting the required values,

⇒ Speed = Distance/Formula

⇒ Speed = 72/2

⇒ Speed = 36

∴ Speed of car = 36 km/hr.

Speed of train :

We know that if we are given the distance and time of a moving object and is asked to find the speed then our required formula is,

Speed = Distance/Time

where,

• Distance = 120 km
• Time = 3 hrs

Using the required formula and substituting the required values,

⇒ Speed = Distance/Formula

⇒ Speed = 120/3

⇒ Speed = 40

∴ Speed of train = 40 km/hr.

Ratio :

We know that,

Ratio = Speed of car/Speed of train

where,

• Speed of car = 36 km/hr
• Speed of train = 40 km/hr

Substituting the values,

⇒ Ratio = Speed of car/Speed of train

⇒ Ratio = 36/40

⇒ Ratio = 9/10

∴ Ratio = 9 : 10.

The ratio of speed of car to the speed of train is 9 : 10.

Explore More :

• Distance = Speed × Time
• Time = Distance/Speed