3. A man walks on a straight road from his home to a market
2.5 km away with a speed of 5 kmh-1. Finding the market
closed, he instantly turns and walks back home with a
speed of 7.5 kmh-1. The average speed of the man over the
interval of time 0 to 40 min is equal to
25
(b) kmh-1
(a) 5 kmh -1
4
30
45
(c)
kmh-1
(d)
kmh-1
4
8
Answers
Answered by
0
Answer:
=
8
45 km/hr
Explanation:
Average speed =
totaltime
totaldistance
Time taken to go to the market =
speed
distance
=
5
2.5
hour=
2
1
hours=30 minutes
Time taken to return back =
speed
distance
=
7.5
2.5
hour=1/3hours=20 minutes
Distance travelled in 10 minutes while returning back=
60
10
×7.5=1.25km ( Speed is constant at 7.5 km/hr )
Hence Distance traveled in 40 minutes(30 mins towards the market and 10 mins towards home) =2.5+1.25=3.75km
So average speed in 0 to 40 minutes =
60
40
hr
3.75km
=
8
45 km/hr
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