At 9 a.m., Opal and Mary raced off together from the starting point of a path. Opal ran at an average speed of 3 m/s. Mary ran at an average speed of 4 m/s. Upon reaching the end of the path, Mary rested for 4 minutes. She then immediately ran back along the same route at 4 m/s. At 9.45 a.m., Opal met Mary.

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 9.45 a.m. = 45 min

Duration that Opal ran = 45 min
Duration that Mary ran = 45 -  4 = 41 min

1 min = 60 s

41 min = 41 x 60 = 2460 s
45 min = 45 x 60 = 2700 s

Distance that Opal ran
= 3 x 2700
= 8100 m

Distance that Mary ran
= 4 x 2460
= 9840 m

Distance that Opal and Mary ran
= 8100 + 9840
= 17940 m

1000 m = 1 km

17940 m = 17940 ÷ 1000 = 17.94 km

(b)
Length of the trail
= 17.94 ÷ 2
= 8.97 km

Answer(s): (a) 17.94 km; (b) 8.97 km