At 7 a.m., Erika and Barbara raced off together from the starting point of a track. Erika ran at an average speed of 1 m/s. Barbara ran at an average speed of 4 m/s. Upon reaching the end of the track, Barbara rested for 3 minutes. She then immediately ran back along the same route at 4 m/s. At 7.40 a.m., Erika met Barbara.

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 7.40 a.m. = 40 min

Duration that Erika ran = 40 min
Duration that Barbara ran = 40 -  3 = 37 min

1 min = 60 s

37 min = 37 x 60 = 2220 s
40 min = 40 x 60 = 2400 s

Distance that Erika ran
= 1 x 2400
= 2400 m

Distance that Barbara ran
= 4 x 2220
= 8880 m

Distance that Erika and Barbara ran
= 2400 + 8880
= 11280 m

1000 m = 1 km

11280 m = 11280 ÷ 1000 = 11.28 km

(b)
Length of the trail
= 11.28 ÷ 2
= 5.64 km

Answer(s): (a) 11.28 km; (b) 5.64 km