Final answer:
Lewis and Clark and their party lost around 5.67 hours of travel time when they decided to take the 17 mile detour, called portage, around the five cascade waterfalls on foot instead of going through the falls by boat.
Step-by-step explanation:
Lewis and Clark and their party took a 17 mile detour, called portage, around the five cascade waterfalls on foot instead of going through the falls by boat. The time they lost during this detour can be estimated based on the average walking speed. Let's assume an average walking speed of 3 miles per hour. So, it would take them approximately 5.67 hours to complete the 17 mile detour. Therefore, Lewis and Clark and their party lost around 5.67 hours of travel time.