At 7 a.m., Risa and Anna raced off together from the starting point of a track. Risa ran at an average speed of 3 m/s. Anna ran at an average speed of 4 m/s. Upon reaching the end of the track, Anna rested for 3 minutes. She then immediately ran back along the same route at 4 m/s. At 7.30 a.m., Risa met Anna.

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 7.30 a.m. = 30 min

Duration that Risa ran = 30 min
Duration that Anna ran = 30 -  3 = 27 min

1 min = 60 s

27 min = 27 x 60 = 1620 s
30 min = 30 x 60 = 1800 s

Distance that Risa ran
= 3 x 1800
= 5400 m

Distance that Anna ran
= 4 x 1620
= 6480 m

Distance that Risa and Anna ran
= 5400 + 6480
= 11880 m

1000 m = 1 km

11880 m = 11880 ÷ 1000 = 11.88 km

(b)
Length of the trail
= 11.88 ÷ 2
= 5.94 km

Answer(s): (a) 11.88 km; (b) 5.94 km