How long will it take 24 grams of plutonium -240 to Decay to 20 gram?

The half-life of plutonium-240 is about 6,560 years. If 24 grams decay to 20 grams, it represents a loss of 4 grams of plutonium. The time it would take for 24 grams to decay to 20 grams would depend on the specific decay rate and is typically calculated using exponential decay equations.