The Decay Constant for Strontium 90 Is λ = 0 $\mathrm { P } _ { 0 }$

Short Answer

The decay constant for strontium 90 is λ = 0.0244, where the time is measured in years. How long will it take for a quantity $\mathrm { P } _ { 0 }$ of strontium 90 to decay to $\frac { 1 } { 3 }$ its original size?
Enter your answer exactly in the form $\frac { \ln a } { \mathrm {~b} }$ where a is a reduced fraction and b is a real number to four decimal places (no units).