At 9 a.m., Ivory and Irene raced off together from the starting point of a course. Ivory ran at an average speed of 3 m/s. Irene ran at an average speed of 4 m/s. Upon reaching the end of the course, Irene rested for 5 minutes. She then immediately ran back along the same route at 4 m/s. At 9.50 a.m., Ivory met Irene.

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 9.50 a.m. = 50 min

Duration that Ivory ran = 50 min
Duration that Irene ran = 50 -  5 = 45 min

1 min = 60 s

45 min = 45 x 60 = 2700 s
50 min = 50 x 60 = 3000 s

Distance that Ivory ran
= 3 x 3000
= 9000 m

Distance that Irene ran
= 4 x 2700
= 10800 m

Distance that Ivory and Irene ran
= 9000 + 10800
= 19800 m

1000 m = 1 km

19800 m = 19800 ÷ 1000 = 19.8 km

(b)
Length of the trail
= 19.8 ÷ 2
= 9.9 km

Answer(s): (a) 19.8 km; (b) 9.9 km