A student fills a graduated cylinder with water. They place a metal rod into the cylinder and the water level rises. They mass the ball on a scale. Using the images below, calculate the density of the rod. Be sure to use precise measurements, significant figures

The independent variable is the type of music.the dependent variable is the pulse rate.the intervening variable is the age of the subject.if the mother does not like rock, her pulse is likely to not increase.the same might be true for the sister.the friend may like rap and gets excited.to establish cause/effect relationship, all of the subjects must be consistent.hope i .