At 7 a.m., Emily and Shiyun raced off together from the starting point of a track. Emily ran at an average speed of 3 m/s. Shiyun ran at an average speed of 4 m/s. Upon reaching the end of the track, Shiyun rested for 6 minutes. She then immediately ran back along the same route at 4 m/s. At 7.50 a.m., Emily 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 7 a.m. to 7.50 a.m. = 50 min

Duration that Emily ran = 50 min
Duration that Shiyun ran = 50 -  6 = 44 min

1 min = 60 s

44 min = 44 x 60 = 2640 s
50 min = 50 x 60 = 3000 s

Distance that Emily ran
= 3 x 3000
= 9000 m

Distance that Shiyun ran
= 4 x 2640
= 10560 m

Distance that Emily and Shiyun ran
= 9000 + 10560
= 19560 m

1000 m = 1 km

19560 m = 19560 ÷ 1000 = 19.56 km

(b)
Length of the trail
= 19.56 ÷ 2
= 9.78 km

Answer(s): (a) 19.56 km; (b) 9.78 km