At 7 a.m., Cindy and Xuan raced off together from the starting point of a route. Cindy ran at an average speed of 2 m/s. Xuan ran at an average speed of 4 m/s. Upon reaching the end of the route, Xuan rested for 6 minutes. She then immediately ran back along the same route at 4 m/s. At 7.25 a.m., Cindy met Xuan.

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 7.25 a.m. = 25 min

Duration that Cindy ran = 25 min
Duration that Xuan ran = 25 -  6 = 19 min

1 min = 60 s

19 min = 19 x 60 = 1140 s
25 min = 25 x 60 = 1500 s

Distance that Cindy ran
= 2 x 1500
= 3000 m

Distance that Xuan ran
= 4 x 1140
= 4560 m

Distance that Cindy and Xuan ran
= 3000 + 4560
= 7560 m

1000 m = 1 km

7560 m = 7560 ÷ 1000 = 7.56 km

(b)
Length of the trail
= 7.56 ÷ 2
= 3.78 km

Answer(s): (a) 7.56 km; (b) 3.78 km