# Radioactive 74344

A type of radioactive element has a mass of 1.125 grams. Upon analysis, he is found to be 405 years old. If this radioactive element decays by half every 45 years, find how many grams of this radioactive element there were 405 years ago.

## Correct answer:

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### You need to know the following knowledge to solve this word math problem:

**algebra**- exponential equation
**arithmetic**- exponentiation
**basic functions**- exponential function
**numbers**- fractions

### Units of physical quantities:

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