At 10 a.m., Cathy and Shiyun raced off together from the starting point of a pathway. Cathy ran at an average speed of 2 m/s. Shiyun ran at an average speed of 4 m/s. Upon reaching the end of the pathway, Shiyun rested for 5 minutes. She then immediately ran back along the same route at 4 m/s. At 10.45 a.m., Cathy 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 10 a.m. to 10.45 a.m. = 45 min

Duration that Cathy ran = 45 min
Duration that Shiyun ran = 45 -  5 = 40 min

1 min = 60 s

40 min = 40 x 60 = 2400 s
45 min = 45 x 60 = 2700 s

Distance that Cathy ran
= 2 x 2700
= 5400 m

Distance that Shiyun ran
= 4 x 2400
= 9600 m

Distance that Cathy and Shiyun ran
= 5400 + 9600
= 15000 m

1000 m = 1 km

15000 m = 15000 ÷ 1000 = 15 km

(b)
Length of the trail
= 15 ÷ 2
= 7.5 km

Answer(s): (a) 15 km; (b) 7.5 km