A Dodge Intrepid and a Mack turck leave an intersection at the same time. The Intrepid heads east at an average speed of 30 miles per hour, while the truck heads south at an average speed of 40 miles per hour. Find an expression for their distance apart d (in miles) at the end of t hours.
I konw d= r*t but I don't know how to use this formula to solve the word problem. Please help!