At 7 a.m., Anna and Betty raced off together from the starting point of a course. Anna ran at an average speed of 2 m/s. Betty ran at an average speed of 4 m/s. Upon reaching the end of the course, Betty rested for 5 minutes. She then immediately ran back along the same route at 4 m/s. At 7.30 a.m., Anna met Betty.

1. Find the total distance covered by the two runners when they met each other. Express your answer in km.
2. Find the length of the trail in km.

(a)
From 7 a.m. to 7.30 a.m. = 30 min

Duration that Anna ran = 30 min
Duration that Betty ran = 30 -  5 = 25 min

1 min = 60 s

25 min = 25 x 60 = 1500 s
30 min = 30 x 60 = 1800 s

Distance that Anna ran
= 2 x 1800
= 3600 m

Distance that Betty ran
= 4 x 1500
= 6000 m

Distance that Anna and Betty ran
= 3600 + 6000
= 9600 m

1000 m = 1 km

9600 m = 9600 ÷ 1000 = 9.6 km

(b)
Length of the trail
= 9.6 ÷ 2
= 4.8 km

Answer(s): (a) 9.6 km; (b) 4.8 km