Uranium-235 (U-235) has a half-life of around 700 million years. U-235 will decay into (after a series of separate decays) Pb-206 (Lead-206). A rock sample is found to have 6.25% (1/16) of its original U-235. a.) How many half-lives have passed?

b.) How many years has this taken?

c.) If there were 30 grams of U-235 originally, how many grams would be left now?

C) electrons encircling a nucleus with neutrons and protons

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 .