# math grade 12

posted by
**kim** on
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2. An isotope of sodium has a half-life of 15 h. A sample of this isotope has a mass of 2 g.

a. [2] Find the mass equation that remains after t hours.

b. [1] Find the mass that remains after 5 hours, to the nearest hundredth.

c. [2] How long, to the nearest hour, will the sample take to decay to a mass of 0.4 grams?

d. [2] Find the average rate of change between 15h and 45h.