Answers to Speed, time and distance question for class vi to viii

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Answers to Speed, time and distance question for class vi to viii
see my previous Blog
 of 12 Nov 2016
 

Solutions:

1. Solution:
Option(C) is correct

Distance = Speed × time

Here time = 2hr 45 min = 114114 hr

Distance = 4×114=114×114=11 km

New Speed =16.5 kmph

Therefore time = DS=1116.5=40 min

2. Solution:
Option(D) is correct

Due to stoppages, it covers 9 km less.

Time taken to cover 9 km = 954×60954×60 = 10 min.

3. Solution:
Option(A) is correct

In same time, they cover 110 km and 90 km respectively.

For the same time speed and distance is inversely proportional.

So ratio of their speed = 110:90110:90 = 11: 9

4. Solution:
Option(B) is correct

Time = 5060=565060=56 hr

Speed = 48 mph

Distance  = S×T=48×56=40S×T=48×56=40 km

Time = 40604060 hr

New speed = 40×32=6040×32=60 kmph

5. Solution:
Option(B) is correct

Let total distance =D=D

Distance travelled at 4 kmph speed =(23)D=(23)D

Distance travelled at 5 kmph speed =(1−23)D=(13)D=(1−23)D=(13)D

Total time =1 hr 24 min = (60+24) min =8460=8460 hr =2115=2115 hr 

We know,

Time=Distance / Speed   & Time=Distance/ Speed

Total time

2115=2/34D+1/35D2115=2/34D+1/35D

2115=2D12+D152115=2D12+D15

84=14D84=14D

D=6 km

6. Explanation:

Speed =		600	m/sec.
		5 x 60

   = 2 m/sec.

Converting m/sec to km/hr (see important formulas section)

=		2 x	18		km/hr
			5

   = 7.2 km/hr.

7. Sachin can cover a distance in 1hr 24 min by covering 2/3 of the distance at 4 kmph and the rest at 5 kmph. The total distance is?

Let total distance =D=D

Distance travelled at 4 kmph speed =(23)D=(23)D

Distance travelled at 5 kmph speed =(1−23)D=(13)D=(1−23)D=(13)D

Total time =1 hr 24 min = (60+24) min =8460=8460 hr =2115=2115 hr 

We know,

Time=Distance/Speed;  Time=Distance/Speed

Total time

2115=2/34D+1/35D2115=2/34D+1/35D

2115=2D12+D152115=2D12+D15

84=14D84=14D

D=6 km

Answer  7 : He takes 3 minutes or to travel a distance of 2.1 kilometers.

8 He can travel 28.3 kilometers in 1 hour 53 minutes.

9. It takes 2 hours 1 minutes or 2s to travel a distance of 199.7 kilometers.

10. It can travel 2085.3 kilometers in 2 hours 16 minutes.

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