Question

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​

Answer 1

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

please follow me