At 7 a.m., Erika and Betty raced off together from the starting point of a track. Erika ran at an average speed of 1 m/s. Betty ran at an average speed of 3 m/s. Upon reaching the end of the track, Betty rested for 4 minutes. She then immediately ran back along the same route at 3 m/s. At 7.25 a.m., Erika met Betty.

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 7.25 a.m. = 25 min

Duration that Erika ran = 25 min
Duration that Betty ran = 25 -  4 = 21 min

1 min = 60 s

21 min = 21 x 60 = 1260 s
25 min = 25 x 60 = 1500 s

Distance that Erika ran
= 1 x 1500
= 1500 m

Distance that Betty ran
= 3 x 1260
= 3780 m

Distance that Erika and Betty ran
= 1500 + 3780
= 5280 m

1000 m = 1 km

5280 m = 5280 ÷ 1000 = 5.28 km

(b)
Length of the trail
= 5.28 ÷ 2
= 2.64 km

Answer(s): (a) 5.28 km; (b) 2.64 km