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A Car with Speed 60 Km/Hr Takes 8 Hours to Travel Some Distance. What Should Be the Increase in the Speed If the Same Distance is to Be Covered in 7 1 2 Hours? - SSC (English Medium) Class 8 - Mathematics

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Question

A car with speed 60 km/hr  takes 8 hours to travel some distance. What should be the increase in the speed if the same distance is to be covered in 7\[\frac{1}{2}\] hours?

Solution

The speed of the car is inversely proportional to the time taken by the car to travel the distance.

Let the speed of the car be s and the time taken by the car to travel the distance be t.

Here, s varies inversely as t i.e. \[s \propto \frac{1}{t}\] . 

∴ \[s = \frac{k}{t}\] , where is k is constant of variation

⇒ s × t = k

When s = 60, t = 8.

∴ k = 60 × 8 = 480

So, the equation of variation is st = 480.

When t = \[7\frac{1}{2}\] h = \[\frac{15}{2}\] h, 

\[s \times \frac{15}{2} = 480\]

⇒ \[s = \frac{480 \times 2}{15}\] = 64 km/h

∴ Increase in the speed = 64 − 60 = 4 km/h

Thus, the increase in the speed of the car is 4 km/h.

  Is there an error in this question or solution?

APPEARS IN

 Balbharati Solution for Balbharati Class 8 Mathematics (2019 to Current)
Chapter 7: Variation
Practice Set 7.3 | Q: 4 | Page no. 40
Solution A Car with Speed 60 Km/Hr Takes 8 Hours to Travel Some Distance. What Should Be the Increase in the Speed If the Same Distance is to Be Covered in 7 1 2 Hours? Concept: Time, Work, Speed.
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