At 11 a.m., Hilda and Zara raced off together from the starting point of a course. Hilda ran at an average speed of 2 m/s. Zara ran at an average speed of 4 m/s. Upon reaching the end of the course, Zara rested for 5 minutes. She then immediately ran back along the same route at 4 m/s. At 11.25 a.m., Hilda 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 11 a.m. to 11.25 a.m. = 25 min

Duration that Hilda ran = 25 min
Duration that Zara 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 Hilda ran
= 2 x 1500
= 3000 m

Distance that Zara ran
= 4 x 1200
= 4800 m

Distance that Hilda and Zara ran
= 3000 + 4800
= 7800 m

1000 m = 1 km

7800 m = 7800 ÷ 1000 = 7.8 km

(b)
Length of the trail
= 7.8 ÷ 2
= 3.9 km

Answer(s): (a) 7.8 km; (b) 3.9 km