Why is it nessesary to have an independent variable that is changed by the experimenter during an experiment

It's important to have a independent variable because if ever thing was the same you will get the same result. Plus you don't want to have same results because it's a experiment . Also you will need a independent variable to do a experiment .

Iassume the answer is 75 feet. inwards to outwards rather than outwards to inwards. probably be 75.hachures are stokes drawn in direction of the steepest slope. a series of short parallel lines drawn on a map to indicate topographic relief. it is actually called hachures on contour lines. the small marks in the center of the feature are called hachures.observe the picture attached