At 7 a.m., Eva and Tina raced off together from the starting point of a course. Eva ran at an average speed of 1 m/s. Tina ran at an average speed of 4 m/s. Upon reaching the end of the course, Tina rested for 5 minutes. She then immediately ran back along the same route at 4 m/s. At 7.25 a.m., Eva met Tina.

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 Eva ran = 25 min
Duration that Tina ran = 25 -  5 = 20 min

1 min = 60 s

20 min = 20 x 60 = 1200 s
25 min = 25 x 60 = 1500 s

Distance that Eva ran
= 1 x 1500
= 1500 m

Distance that Tina ran
= 4 x 1200
= 4800 m

Distance that Eva and Tina ran
= 1500 + 4800
= 6300 m

1000 m = 1 km

6300 m = 6300 ÷ 1000 = 6.3 km

(b)
Length of the trail
= 6.3 ÷ 2
= 3.15 km

Answer(s): (a) 6.3 km; (b) 3.15 km