At 10 a.m., Usha and Opal raced off together from the starting point of a track. Usha ran at an average speed of 1 m/s. Opal ran at an average speed of 2 m/s. Upon reaching the end of the track, Opal rested for 5 minutes. She then immediately ran back along the same route at 2 m/s. At 10.40 a.m., Usha met Opal.

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 10 a.m. to 10.40 a.m. = 40 min

Duration that Usha ran = 40 min
Duration that Opal 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 Usha ran
= 1 x 2400
= 2400 m

Distance that Opal ran
= 2 x 2100
= 4200 m

Distance that Usha and Opal ran
= 2400 + 4200
= 6600 m

1000 m = 1 km

6600 m = 6600 ÷ 1000 = 6.6 km

(b)
Length of the trail
= 6.6 ÷ 2
= 3.3 km

Answer(s): (a) 6.6 km; (b) 3.3 km