Answer: it will take 1.8 hours
Step-by-step explanation:
The time taken for a journey on a motorway varies inversely as the average speed for the journey. Let t represent taken for the journey. Let s represent the average speed. If we introduce a constant of varistion, k, the expression becomes
t = k/s
The journey takes 1.5 h when the average speed is 54 miles per hour. This means that
1.5 = k/54
k = 54 × 1.5 = 81
The equation becomes
t = 81/s
Therefore, when the average speed is 45 miles per hour, the time taken would be
t = 81/45
t = 1.8
