Selina Solutions Concise Mathematics Class 6 Chapter 17 Idea of Speed, Distance and Time Exercise 17(A) help students get a clear idea of topics and the steps to be followed in solving problems with ease. The solutions prepared in an understandable language, by expert faculty at BYJUâ€™S, help students to achieve high marks in the final examinations. Shortcut tips and formulas are covered in a stepwise manner, for a better understanding of the concepts. Selina Solutions Concise Mathematics Class 6 Chapter 17 Idea of Speed, Distance and Time Exercise 17(A) PDF, can be downloaded from the available links below.

## Selina Solutions Concise Mathematics Class 6 Chapter 17: Idea of Speed, Distance and Time Exercise 17(A) Download PDF

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#### Exercise 17(A)

**1. A train covers 51 km in 3 hours. Calculate its speed. How far does the train go in 30 minutes?**

**Solution:**

Given

A train covers 51 km in 3 hours

So, distance = 51 km

Time = 3 hours

Hence,

Speed = 51 km/ 3 hours

We get,

= 17 km/h

Now for 30 minutes

Speed = 17 km/h

Time = 0.5 hours

Hence,

Distance = 17 Ã— 0.5

We get,

= 8.5 km

Therefore, train covered 8.5 km in 30 minutes

**2. A motorist travelled the distance between two towns, which is 65 km, in 2 hours and 10 minutes. Find his speed in metre per minute.**

**Solution:**

Given

A motorist travelled the distance 65 km in 2 hours and 10 minutes

So, distance = 65 km

Time = 2 hours 10 minutes

Hence,

Speed = 65 km / (2 hours + 10 minutes)

We know that,

1 km = 1000 m

1 hour = 60 min

= 65 (1000 m) / [2 (60 min) + 10 min]

= 65000 m/130 min

We get,

= 500 m/min

Therefore, the speed of a motorist in meter per minute is 500 m/min

**3. A train travels 700 metres in 35 seconds. What is its speed in km/h?**

**Solution:**

Given

A train travels 700 metres in 35 seconds

So, distance = 700 m

Time = 35 sec

Hence,

Speed = 700 m / 35 sec

1000 m = 1 km

1 m = 0.001 km

700 m = 0.001 Ã— 700

= 0.7 km

3600 seconds = 1 hour

1 sec = 1 / 3600 hour

35 sec = 35 / 3600

Now,

Speed = Distance / Time

= [0.7 / (35/ 3600**)]**

We get,

**= (0.7 **Ã— 3600) / 35

= 2520 / 35

= 72 km/h

Therefore, the speed of train is 72 km/h

**4. A racing car covered 600 km in 3 hours 20 minutes. Find its speed in metre per second. How much distance will the car cover in 50 sec?**

**Solution:**

Given

A racing car covered 600 km in 3 hours and 20 minutes

So, distance = 600 km

Time = 3 hours 20 minutes

Hence,

Speed = 600 km / (3 hours + 20 minutes)

= 600 (1000m) / [3(60 min) + 20 min]

We get,

= 600000m / 200 min

= 600000m / 200 (60 sec)

We get,

= 600000 / 12000 sec

= 50 m / sec

Thus, speed in meter per second is 50 m / sec

Now, the distance covered by car in 50 sec is calculated as below

Speed = 50 m / sec

Time = 50 sec

Hence,

Distance = 50 Ã— 50

= 2500 m

= 2.5 km

Therefore, the distance covered by car in 50 seconds is 2.5 km

**5. Rohit goes 350 km in 5 hours. Find:**

**(i) his speed **

**(ii) the distance covered by Rohit in 6.2 hours**

**(iii) the time taken by him to cover 210 km**

**Solution:**

(i) his speed

Given

Rohit goes 350 km in 5 hours

So, distance = 350 km

Time = 5 hours

Hence,

Speed = 350 km / 5 hours

We get,

= 70 km/h

Hence, Rohit speed is 70 km/h

(ii) the distance covered by Rohit in 6.2 hours

Given

Rohit goes 350 km in 5 hours

So, distance = 350 km

Time = 5 hours

Hence,

Speed = 350 km / 5 hours

We get,

= 70 km/h

Now, the distance covered by Rohit in 6.2 hours is calculated as below

Speed = 70 km/h

Time = 6.2 hours

Hence,

Distance = 70 Ã— 6.2

= 434 km

Therefore, Rohit covers 434 km in 6.2 hours

(iii) the time taken by him to cover 210 km

Given

Rohit goes 350 km in 5 hours

So, distance = 350 km

Time = 5 hours

Hence,

Speed = 350 km / 5 hours

We get,

= 70 km/h

Now, the time taken by Rohit to cover 210 km is calculated as below

Distance = 210 km

Speed = 70 km/h

Hence,

Time = 210 km / 70 km/h

= 3 hours

Therefore, the time taken by Rohit to cover 210 km is 3 hours

**6. A boy drives his scooter with a uniform speed of 45 km/h. Find:**

**(i) the distance covered by him in 1 hour 20 min**

**(ii) the time taken by him to cover 108 km**

**(iii) the time taken to cover 900 m**

(i) the distance covered by him in 1 hour 20 min

Given

Speed of scooter is 45 km/h

Speed = 45 km/h

Time = 1 hours 20 minutes

Hence,

Distance = 45 Ã— (1 + 20 / 60)

= 45 Ã— (1 + 1 / 3)

We get,

= 45 Ã— 4 / 3

= 15 Ã— 4

= 60

Hence, the distance covered by a boy in 1 hour 20 minutes is 60 km

(ii) the time taken by him to cover 108 km

Given

Speed of scooter is 45 km/h

So, speed = 45 km/h

Distance = 108 km

Hence,

Time = 108 km / 45 km/h

We get,

= 12 / 5 h

=h

This is equal to,

= 2 hours (2 / 5) Ã— 60 min

= 2 hours (2 Ã— 12) min

= 2 hours 24 min

Hence, the time taken by a boy to cover 108 km distance is 2 hours 24 min

(iii) the time taken to cover 900 m

Given

Speed of scooter is 45 km/h

So, speed = 45 km/h

Distance = 900 m

Hence,

Time = 900 m / 45 km/h

= (900 / 1000) Ã— 1 / 45

We get,

= (9 / 10) Ã— (1 / 45)

= 1 / 50 h

= (1 / 50) Ã— 60 min

= 6 / 5 min

This can be written as,

= 1 and 1 / 5 min

= 1 min (1 / 5) Ã— 60 sec

We get,

= 1 min 12 sec

Hence, the time taken by a boy to cover 900 m is 1 min 12 sec

**7. I travel a distance of 10 km and come back in 2 Â½ hours. What is my speed?**

**Solution:**

Given

10 km distance travelled twice in 2 Â½ hours

So, distance = 10 km + 10 km

= 20 km

Time = 2 Â½ hours

This can be written as,

Time = 5 / 2 hours

Hence,

Speed = [20 km / (5 / 2 hours)]

= (20 Ã— 2) / 5

We get,

= 40 / 5

= 8 km/h

Hence, the speed of a person to cover a distance of 10 km twice is 8 km/h

**8. A man walks a distance of 5 km in 2 hours. Then he goes in a bus to a nearby town, which is 40 km, in further 2 hours. From there, he goes to his office in an autorickshaw, a distance of 5 km, in Â½ hour. What was his average speed during the whole journey?**

**Solution:**

Given

A man walks a distance of 5 km in 2 hours

40 km distance is covered by bus in 2 hours

5 km distance is covered by autorickshaw in Â½ hour

Hence,

Total distance covered by a man during whole journey is calculated as below

Total distance = 5 km + 40 km + 5 km

= 50 km

Total time taken by a man during whole journey

Total time = 2 + 2 + 1/2

= (4 + 4 + 1) / 2

We get,

= 9 / 2 hours

Hence,

Average speed = 50 km / (9 / 2) hours

= (50 Ã— 2) / 9 km/h

= 100 / 9 km/h

=Â km/h

Therefore, the average speed taken by a man during whole journey isÂ km/h

**9. Jagan went to another town such that he covered 240 km by a car going at 60 kmh ^{-1}. Then he covered 80 km by a train, going at 100 kmh^{-1} and the rest 200 km, he covered by a bus, going at 50 kmh^{-1}. What was his average speed during the whole journey?**

**Solution:**

Given

Jagan covered 240 km distance by a car at 60 km/h

He travelled 80 km distance by train at 100 km/h

He travelled 200 km distance by a bus at 50 km/h

Hence,

Total distance travelled by Jagan = 240 km + 80 km + 200 km

= 520 km

Now, total time taken by Jagan during whole journey is shown below

Time taken by car = 240 km / 60 km/h

= 4 hours

Time taken by a train = 80 km / 100 km/h

= 4 / 5 hours

Time taken by bus = 200 km / 50 km/h

= 4 hours

So, total time taken = 4 + 4 / 5 + 4

= (20 + 4 + 20) / 5

We get,

= 44 / 5 hours

Hence,

Average speed = total distance / total time

= 520 km / (44 / 5) hours

= [(520 Ã— 5) / 44] km/h

= (130 Ã— 5) / 11 km/h

= 650 / 11 km/h

=Â km/h

Hence, the average speed during the whole journey isÂ km/h

**10. The speed of sound in air is about 330 ms ^{-1}. Express this speed in kmh^{-1}. How long will the sound take to travel 99 km?**

**Solution:**

Given

Speed of sound in air = 330 m/sec

So, speed = 330 m/sec

Distance = 99 km

= 99 Ã— 1000

We get,

= 99000 m

Hence,

Time = [(99000 m) / (330 m/sec)]

= 9900 / 33 sec

We get,

= 300 sec

= 5 min

Hence, the time taken by the sound to travel 99 km is 5 min

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