Answer:
Step-by-step explanation:
The formula for determining the perimeter of a rectangle is expressed as
Perimeter = 2(L + W)
The garden measures 30m × 70m. The perimeter would be
Perimeter = 2(30 + 70) = 200m
If Karen's brother is running 2 laps around the inner edge of the walkway, then the total distance covered is 200 × 2 = 400m
Converting to km, it becomes
400/1000 = 0.4km
If he runs 2 times faster than Karen, then his speed is 2 × 4 = 8km/h
Time = distance/speed
Time spent in running the 2 laps is
0.4/8 = 0.05 hours
Converting to minutes, it becomes
0.05 × 60 = 3 minutes
Since the walkway is 5m, if Karen is running one lap around the outer edge of the walkway, the total length would be (70 + 5 + 5) = 80m
The width would be (30 + 5 + 5) = 40m. The perimeter is
2(80 + 40) = 240 m
Converting to kilometers, it becomes
240/100 = 0.24 km
Time taken by Karen to run 0.24km is
0.24/4 = 0.06 hours
Converting to minutes, it becomes
0.06 × 60 = 3.6 minutes
The difference in time is
3.6 - 3 = 0.6 minutes
Karen's brother finish his run in
0.6 minutes earlier than Karen.
