Which best describes the purpose of a controlled experiment? to make sure the results of the experiment support the hypothesis to prevent a dangerous condition resulting from a reaction to examine whether one variable causes a change in another to prevent an undesired change in a variable

Johnny rode his bike to a friends house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was unable to play. what was his displacement for the total bike ride trip? what could you use as a reference point ? show the steps to solve this problem.