At 11 a.m., Jaslyn and Risa raced off together from the starting point of a route. Jaslyn ran at an average speed of 1 m/s. Risa ran at an average speed of 4 m/s. Upon reaching the end of the route, Risa rested for 5 minutes. She then immediately ran back along the same route at 4 m/s. At 11.40 a.m., Jaslyn met Risa.

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 11 a.m. to 11.40 a.m. = 40 min

Duration that Jaslyn ran = 40 min
Duration that Risa ran = 40 -  5 = 35 min

1 min = 60 s

35 min = 35 x 60 = 2100 s
40 min = 40 x 60 = 2400 s

Distance that Jaslyn ran
= 1 x 2400
= 2400 m

Distance that Risa ran
= 4 x 2100
= 8400 m

Distance that Jaslyn and Risa ran
= 2400 + 8400
= 10800 m

1000 m = 1 km

10800 m = 10800 ÷ 1000 = 10.8 km

(b)
Length of the trail
= 10.8 ÷ 2
= 5.4 km

Answer(s): (a) 10.8 km; (b) 5.4 km