At 9 a.m., Usha and Irene raced off together from the starting point of a route. Usha ran at an average speed of 1 m/s. Irene ran at an average speed of 2 m/s. Upon reaching the end of the route, Irene rested for 3 minutes. She then immediately ran back along the same route at 2 m/s. At 9.50 a.m., Usha 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 Usha ran = 50 min
Duration that Irene ran = 50 -  3 = 47 min

1 min = 60 s

47 min = 47 x 60 = 2820 s
50 min = 50 x 60 = 3000 s

Distance that Usha ran
= 1 x 3000
= 3000 m

Distance that Irene ran
= 2 x 2820
= 5640 m

Distance that Usha and Irene ran
= 3000 + 5640
= 8640 m

1000 m = 1 km

8640 m = 8640 ÷ 1000 = 8.64 km

(b)
Length of the trail
= 8.64 ÷ 2
= 4.32 km

Answer(s): (a) 8.64 km; (b) 4.32 km