At 7 a.m., Cindy and Emily raced off together from the starting point of a track. Cindy ran at an average speed of 3 m/s. Emily ran at an average speed of 4 m/s. Upon reaching the end of the track, Emily rested for 5 minutes. She then immediately ran back along the same route at 4 m/s. At 7.50 a.m., Cindy met Emily.

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 Cindy ran = 50 min
Duration that Emily 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 Cindy ran
= 3 x 3000
= 9000 m

Distance that Emily ran
= 4 x 2700
= 10800 m

Distance that Cindy and Emily ran
= 9000 + 10800
= 19800 m

1000 m = 1 km

19800 m = 19800 ÷ 1000 = 19.8 km

(b)
Length of the trail
= 19.8 ÷ 2
= 9.9 km

Answer(s): (a) 19.8 km; (b) 9.9 km