Plutonium 241 has a decay rate of 4.8 % per year. How many years will it take a 50 kg sample to deca

Plutonium 241 has a decay rate of 4.8 % per year. How many years will it take a 50 kg sample to decay to 10 kg?

Since 4.8% is 0.048, we have decay as:
50 * (1 - 0.048)^n = 10
0.952^n = 0.2

Typing this into our math engine, we get:
n = 32.7186 years