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#35155

applications

exponential

hard

90 sec

A certain type of radioactive isotope decays at a constant annual rate. In $2000$ , a sample contained $500$ grams of the isotope. In $2010$ , the sample contained $300$ grams. Assuming the decay is exponential, how many grams of the isotope were in the sample in $1990$ ? Round your answer to the nearest whole number.

• Up to 5 characters (6 if negative). Only numbers, decimal (.), fraction (/), negative (-).
• Fractions must be in lowest terms.
• Mixed numbers must be converted to improper fractions.