Mathematics for IGCSE & O level - Proportion (Section 2 - No. 19)
The time taken for a journey, *t*, is inversely proportional to the speed, *s*. If *t* is 3 hours when *s* is 60 km/h, find *s* when *t* is 2 hours.
40 km/h
90 km/h
100 km/h
120 km/h
解释
t = k/s, 3 = k/60, k=180; s=180/t; when t=2, then s=180/2 = 90km/h.