Question 25
Linear and Simultaneous EquationsA man runs a distance of 9km at a constant speed for the first 4km and then 2km/h faster for the rest of the distance. The whole run takes him one hour. His average speed for the first 4km is
- A.6km/h
- B.8km/h
- C.9km/h
- D.11km/h
- E.13km/h.
Show the answer and explanation
Answer: B (8km/h)
Explanation
With speed v: 4/v + 5/(v + 2) = 1, which gives v² − 7v − 8 = 0, so v = 8km/h.