At 9 a.m., Usha and Yoko raced off together from the starting point of a route. Usha ran at an average speed of 1 m/s. Yoko ran at an average speed of 3 m/s. Upon reaching the end of the route, Yoko rested for 3 minutes. She then immediately ran back along the same route at 3 m/s. At 9.35 a.m., Usha met Yoko.

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 9.35 a.m. = 35 min

Duration that Usha ran = 35 min
Duration that Yoko ran = 35 -  3 = 32 min

1 min = 60 s

32 min = 32 x 60 = 1920 s
35 min = 35 x 60 = 2100 s

Distance that Usha ran
= 1 x 2100
= 2100 m

Distance that Yoko ran
= 3 x 1920
= 5760 m

Distance that Usha and Yoko ran
= 2100 + 5760
= 7860 m

1000 m = 1 km

7860 m = 7860 ÷ 1000 = 7.86 km

(b)
Length of the trail
= 7.86 ÷ 2
= 3.93 km

Answer(s): (a) 7.86 km; (b) 3.93 km