We have here an exponential decay. In this case, we have to use the formula:
[tex]y=a(1-r)^x^{}[/tex]
Where:
a = initial value (in this case, 360 grams)
r = decay rate (in this case, we have 50/100= 0.5.
x = number of time intervals that have passed (in this case, 4 hours).
Then, we have that:
[tex]y=360\cdot(1-0.5)^4\Rightarrow y=300\cdot(0.5)^4\Rightarrow y=22.5[/tex]
Hence, after four hours there will be 22.5 grams of the radioactive material.
