At 11 a.m., Shiyun and Xuan raced off together from the starting point of a course. Shiyun ran at an average speed of 1 m/s. Xuan ran at an average speed of 3 m/s. Upon reaching the end of the course, Xuan rested for 3 minutes. She then immediately ran back along the same route at 3 m/s. At 11.50 a.m., Shiyun met Xuan.

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 11 a.m. to 11.50 a.m. = 50 min

Duration that Shiyun ran = 50 min
Duration that Xuan ran = 50 -  3 = 47 min

1 min = 60 s

47 min = 47 x 60 = 2820 s
50 min = 50 x 60 = 3000 s

Distance that Shiyun ran
= 1 x 3000
= 3000 m

Distance that Xuan ran
= 3 x 2820
= 8460 m

Distance that Shiyun and Xuan ran
= 3000 + 8460
= 11460 m

1000 m = 1 km

11460 m = 11460 ÷ 1000 = 11.46 km

(b)
Length of the trail
= 11.46 ÷ 2
= 5.73 km

Answer(s): (a) 11.46 km; (b) 5.73 km