At 10 a.m., Yen and Zara raced off together from the starting point of a route. Yen ran at an average speed of 1 m/s. Zara ran at an average speed of 4 m/s. Upon reaching the end of the route, Zara rested for 3 minutes. She then immediately ran back along the same route at 4 m/s. At 10.45 a.m., Yen met Zara.

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 Yen ran = 45 min
Duration that Zara ran = 45 -  3 = 42 min

1 min = 60 s

42 min = 42 x 60 = 2520 s
45 min = 45 x 60 = 2700 s

Distance that Yen ran
= 1 x 2700
= 2700 m

Distance that Zara ran
= 4 x 2520
= 10080 m

Distance that Yen and Zara ran
= 2700 + 10080
= 12780 m

1000 m = 1 km

12780 m = 12780 ÷ 1000 = 12.78 km

(b)
Length of the trail
= 12.78 ÷ 2
= 6.39 km

Answer(s): (a) 12.78 km; (b) 6.39 km