Aparticle decays at a rate of 0.45% annually. assume and initial amount of 300 mg. (
a. how much of the particle remains after 60 years? (
b. what is the half-life of the particle?

The increase is an exponential increase in a multiplier
and as decimal 1.0045

Final Value = Initial Value × 
Final value = 
Final value = 393 mg (to the nearest whole number)

Half life = 0.5 years
Final value = =301 mg

The first one, i believe, would be correct. all the others have one thing in common, and that's that they have repeating numbers. in the second one, x and y have repeating 6's and 3's, and in the third, x and y have repeating 6's as well. in the last one, there are repeating 3's. the first one has no repeating numbers.