Question 286906
If "your friend drives for 3.5 hours at an average speed of 60 miles per hour", then your friend has driven {{{D=rt=60*3.5=210}}} miles. So you need to drive {{{450-210=240}}} more miles to complete the trip.



Now using {{{D=rt}}}, plug in D=240 (the amount of distance you need to cover) and t=4 (the amount of time you want to travel) to get {{{240=r*4}}}. Divide both sides by 4 to get {{{240/4=r}}} and reduce to get {{{r=60}}}


So you need to average 60 mph.