Mathematics for IGCSE & O level - Proportion (Section 3 - No. 4)
The time, *t*, taken for a journey is inversely proportional to the speed, *s*. If a journey takes 4 hours at a speed of 60 km/h, how long will the journey take at a speed of 80 km/h?
2 hours
3 hours
4 hours
6 hours
คำอธิบาย
Since t is inversely proportional to s, t = k/s. When t=4 and s=60, k=240. When s=80, t=240/80=3