At 8 a.m., Anna and Shiyun raced off together from the starting point of a route. Anna ran at an average speed of 1 m/s. Shiyun ran at an average speed of 3 m/s. Upon reaching the end of the route, Shiyun rested for 6 minutes. She then immediately ran back along the same route at 3 m/s. At 8.40 a.m., Anna met Shiyun.

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 8 a.m. to 8.40 a.m. = 40 min

Duration that Anna ran = 40 min
Duration that Shiyun ran = 40 -  6 = 34 min

1 min = 60 s

34 min = 34 x 60 = 2040 s
40 min = 40 x 60 = 2400 s

Distance that Anna ran
= 1 x 2400
= 2400 m

Distance that Shiyun ran
= 3 x 2040
= 6120 m

Distance that Anna and Shiyun ran
= 2400 + 6120
= 8520 m

1000 m = 1 km

8520 m = 8520 ÷ 1000 = 8.52 km

(b)
Length of the trail
= 8.52 ÷ 2
= 4.26 km

Answer(s): (a) 8.52 km; (b) 4.26 km