Question

a rectangle field is 90m by 70m . A man walks around it at the rate of 4km per hour . what time will he take in making 5 rounds?

Answer 1

length L of the rectangle =90m
breadth B of the rectangle =70m
perimeter of the rectangle = 2( L +B)
=2(90+70)
=2x160
=320m
total distance to travel 5 rounds =5x320=1600m
let the time taken by the man to walk around the perimeter of the rectangle =T
speed =4km/h=4x1000/3600sec [convert to metre per second and 1hour =60x60seconds ]
speed =1.12m/sec
speed = perimeter /time
1.12=320/T
T=1600/1.12
T=1429second
T=1429/60
T=24mins (approx)
hence the time taken =24mins

Answer 2

Answer:

Step-by-step explanation:

Perimeter of the rectangle is 90 + 90 + 70 +70 = 160 + 160 =320 m

In km we have 320/ 1000 = 0.320 km because 1000m = 1 km

So his speed = 4 km / hr = 4 km / 60 min = 1 km in 15 min .

5 rounds implies 5 ( 0.320 ) = 1.6 km

So if 1 km is 15 min then 1.6 km 

15 × 1.6 min = 24 min

Hence the person takes 24 min .

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