At 10 a.m., Usha and Vanessa raced off together from the starting point of a course. Usha ran at an average speed of 2 m/s. Vanessa ran at an average speed of 4 m/s. Upon reaching the end of the course, Vanessa rested for 3 minutes. She then immediately ran back along the same route at 4 m/s. At 10.50 a.m., Usha met Vanessa.

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 10.50 a.m. = 50 min

Duration that Usha ran = 50 min
Duration that Vanessa 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
= 2 x 3000
= 6000 m

Distance that Vanessa ran
= 4 x 2820
= 11280 m

Distance that Usha and Vanessa ran
= 6000 + 11280
= 17280 m

1000 m = 1 km

17280 m = 17280 ÷ 1000 = 17.28 km

(b)
Length of the trail
= 17.28 ÷ 2
= 8.64 km

Answer(s): (a) 17.28 km; (b) 8.64 km