# Geometry Word Problem

• May 2nd 2007, 04:47 AM
whytechocolate01
Geometry Word Problem
Use an indirect proof to show that John exceeded the 55mph speed limit if he left his house at 8:15 a.m. and arrived at his office 60 miles away at 9:00 a.m. Write the proof using the paragraph method.

Pleeeeaaaasssseeee explain this to me!
• May 2nd 2007, 08:24 AM
Jhevon
Quote:

Originally Posted by whytechocolate01
Use an indirect proof to show that John exceeded the 55mph speed limit if he left his house at 8:15 a.m. and arrived at his office 60 miles away at 9:00 a.m. Write the proof using the paragraph method.

Pleeeeaaaasssseeee explain this to me!

well, if he travelled 60 miles in 45 mins, it means his average speed was 80 mph. therefore, at some point he must have been going at 80 mph for it to be the average. thus he exceeded 55 mph at some point. if you know the mean value theorem you canuse that to prove it elegantly--that's calculus though (i think, i never learnt it till calculus), so if you're not in calculus, forget about it