At 10 a.m., Shiyun and Winnie raced off together from the starting point of a route. Shiyun ran at an average speed of 2 m/s. Winnie ran at an average speed of 4 m/s. Upon reaching the end of the route, Winnie rested for 3 minutes. She then immediately ran back along the same route at 4 m/s. At 10.40 a.m., Shiyun met Winnie.

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 10.40 a.m. = 40 min

Duration that Shiyun ran = 40 min
Duration that Winnie ran = 40 -  3 = 37 min

1 min = 60 s

37 min = 37 x 60 = 2220 s
40 min = 40 x 60 = 2400 s

Distance that Shiyun ran
= 2 x 2400
= 4800 m

Distance that Winnie ran
= 4 x 2220
= 8880 m

Distance that Shiyun and Winnie ran
= 4800 + 8880
= 13680 m

1000 m = 1 km

13680 m = 13680 ÷ 1000 = 13.68 km

(b)
Length of the trail
= 13.68 ÷ 2
= 6.84 km

Answer(s): (a) 13.68 km; (b) 6.84 km