At 9 a.m., Risa and Fiona raced off together from the starting point of a course. Risa ran at an average speed of 3 m/s. Fiona ran at an average speed of 4 m/s. Upon reaching the end of the course, Fiona rested for 6 minutes. She then immediately ran back along the same route at 4 m/s. At 9.40 a.m., Risa met Fiona.

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 9 a.m. to 9.40 a.m. = 40 min

Duration that Risa ran = 40 min
Duration that Fiona ran = 40 -  6 = 34 min

1 min = 60 s

34 min = 34 x 60 = 2040 s
40 min = 40 x 60 = 2400 s

Distance that Risa ran
= 3 x 2400
= 7200 m

Distance that Fiona ran
= 4 x 2040
= 8160 m

Distance that Risa and Fiona ran
= 7200 + 8160
= 15360 m

1000 m = 1 km

15360 m = 15360 ÷ 1000 = 15.36 km

(b)
Length of the trail
= 15.36 ÷ 2
= 7.68 km

Answer(s): (a) 15.36 km; (b) 7.68 km