Find the radius of a circle with a circumference of 18.58 feet

The base of a triangle is 8 1 3 meters and the height of the triangle is the fourth root of 16 meters meters. what is the area of the triangle?

This is a map of the mars exploration rover opportunity predicted landing site on mars. the scale is 1cm : 9.4km. what are the approximate measures of the actual length and width of the ellipse? i mostly need to know how to set it up : )

Atrain leaves little? rock, arkansas, and travels north at 90 kilometers per hour. another train leaves at the same time and travels south at 80 kilometers per hour. how long will it take before they are 680 kilometers? apart?