Final answer:
The amount of radioactive plutonium left after 28 weeks, starting with 1,248 grams and a half-life of 7 weeks, would be 312 grams.
Step-by-step explanation:
The half-life of plutonium is 7 weeks. This means that after 7 weeks, half of the radioactive plutonium will decay and half will remain. After another 7 weeks, half of the remaining plutonium will decay and so on.
In this case, you are starting with 1,248 grams of plutonium. Since the half-life is 7 weeks, after 7 weeks, half of the initial amount will remain, which is 1,248 grams / 2 = 624 grams
After another 7 weeks, half of the remaining amount will decay, which is 624 grams / 2 = 312 grams. This process will continue every 7 weeks until the amount is negligibly small.
Therefore, after 28 weeks, the amount of radioactive plutonium remaining will be 312 grams.