At 11 a.m., Abi and Shiyun raced off together from the starting point of a track. Abi ran at an average speed of 1 m/s. Shiyun ran at an average speed of 2 m/s. Upon reaching the end of the track, Shiyun rested for 5 minutes. She then immediately ran back along the same route at 2 m/s. At 11.50 a.m., Abi 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 11 a.m. to 11.50 a.m. = 50 min

Duration that Abi ran = 50 min
Duration that Shiyun 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 Abi ran
= 1 x 3000
= 3000 m

Distance that Shiyun ran
= 2 x 2700
= 5400 m

Distance that Abi and Shiyun 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