A cross-country runner runs at 8 km/h on a bearing of 150° T for 45 mins, then changes direction to a bearing of 053° T and runs for 80 mins until he is due east of the starting point.
a) (i) How far was the second part of the run?
(ii) What was his speed for this section?
Hello Mr RayonCall the starting point , the point where he changes direction , and his final position . Then we have:
- km
(i)
- Use the angle sum of triangle to calculate
- Use the Sine Rule to calculate :
(ii) This distance takes mins = hours. So divide the distance by this time, , to find his speed in km/h.
Grandad