A sample of a radioactive isotope had an initial mass of 650 mg in the year 2003 and decays exponentially over time. A measurement in the year 2005 found that the sample's mass had decayed to 490 mg. What would be the expected mass of the sample in the year 2007, to the nearest whole number?

330 mg

Step-by-step explanation:

at the start of the year 2003 the starting mass is (650) mg
2 years have passed and the mass now is  (490) mg
the subtraction of these will let us know how many MG decayed
650 - 490 = 160 mg
so in 2 years 160 mg decayed, how about in one year?
160/ 2 = 80 mg per year
we started at 2003 and we need the end result in 2007 which is
2007- 2003 = 4 years
4 multiplied by 80 = 320 mg decayed in 4 years
by subtracting it from 650 we will get the result
650 - 320 = 330 mg!

right

step-by-step explanation: