Show that the time it takes a radioactive isotope (such as the isotope given in the previous homework problem) to decay to 70% of it's original amount doesn't depend on the initial amount of the substance, but rather on only the decay constant k. To do this, start with the formula A(t) = Anekt and find a formula, in terms of k only, to determine how long it takes a radioactive isotope to decay to 70% of it's original amount. t = (Note: Finding the time it takes a material "to decay to 70% of it's original amount" is different than finding the time it takes for "70 % of the original amount of material to decay". Can you tell why they are different?)

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