At 10 a.m., Shiyun and Betty raced off together from the starting point of a path. Shiyun ran at an average speed of 1 m/s. Betty ran at an average speed of 2 m/s. Upon reaching the end of the path, Betty rested for 5 minutes. She then immediately ran back along the same route at 2 m/s. At 10.50 a.m., Shiyun 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 10 a.m. to 10.50 a.m. = 50 min

Duration that Shiyun ran = 50 min
Duration that Betty ran = 50 -  5 = 45 min

1 min = 60 s

45 min = 45 x 60 = 2700 s
50 min = 50 x 60 = 3000 s

Distance that Shiyun ran
= 1 x 3000
= 3000 m

Distance that Betty ran
= 2 x 2700
= 5400 m

Distance that Shiyun and Betty ran
= 3000 + 5400
= 8400 m

1000 m = 1 km

8400 m = 8400 ÷ 1000 = 8.4 km

(b)
Length of the trail
= 8.4 ÷ 2
= 4.2 km

Answer(s): (a) 8.4 km; (b) 4.2 km