Question

A journey takes 4 hours 30 minutes at a speed of 60 km/h. How long will the same
journey take at a speed of 15 m/ sec? [Hint. 15 m/sec = (15*18/5) km/h=54km/h]​

Answer 1

• Given

• Time taken in a journey = 4 hours 30 minutes at a speed of 60 km/h
• New speed = 15 m/s

• To find

• Time taken if speed is 15 m/s

• Solution

• Time = 4 hours 30 mins

As we know,

⇒ 1 min = 1/60 hr

Divide 30 mins by 60.

⇒ 30/60

⇒ 10/20

⇒ 1/2 hr

Now add 1/2 hr and 4 hr

⇒ 4 + 1/2

⇒ 4.5 hours

• Time = 4.5 hours
• Speed = 60 km/h

Distance = Speed × Time

⇒ 60 × 4.5

⇒ 270 km

• Distance = 270 km

• New speed = 15 km/h

• Distance = 270 m/s

⇒ 270 × 18/5 = 54 km/h

Time = Distance/Speed

Substitute the given values,

⇒ 270/54

⇒ 5 hours

• If the speed is 15 m/s or 54 km/h the journey will take 5 hours.

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Know More

• To convert m/s to km/h multiply the given value by 18/5.
• To convert km/h to m/s multiply the given value by 5/18.

• Distance is the path travelled by a body.
• Speed is the rate at which an object travels a particular distance.
• Speed = Distance/Time