



 
Hi Nigel. Let's think of the two different situations: travelling slow and travelling fast: d = vt t = d/v, so t_{s } = d/v_{s } and t_{f } = d/v_{f } since d is the same distance in both cases. What you are asked for is the decrease in time. That's the difference t_{s }  t_{f }: t_{s }  t_{f } = d/v_{s}  d/v_{f } Now, you also know that the increase in speed (v_{f }  v_{s}) is x, so can you finish the solution by substituting v for v_{s } and v + x for v_{f } and then simplifying? Hope this helps,  


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