Radioactive Decay of Magnesium-28 mathbf(R) & mathbf(t) (hours) 1 & 0 0.5 & 21 0.25 & 42 0.125 & 63 0.0625 & 84 0.03125 & 105 0.015625 & 126 Radioactive Decay of Magnesium-28 The graph shows remaining portion of Magnesium-28 measured for 125 hours. How many hours long is the half-life of Magnesium-28?

#ExplanationThe half-life of a substance undergoing radioactive decay is the time it takes for half of the substance to decay. In other words, it's the time it takes for the remaining portion of the substance to decrease by half.Looking at the table, we can see that the remaining portion of Magnesium-28 ( ) decreases by half every 21 hours. This is evident from the fact that decreases from 1 to 0.5 between 0 and 21 hours, from 0.5 to 0.25 between 21 and 42 hours, and so on.Therefore, the half-life of Magnesium-28 is 21 hours.#Answer21 hours