The half-life of charged pions, + and s, is 1.8 10 -8 s;

The half-life of charged pions, π⁺ and π^– s, is 1.8 × 10^-8 s; i.e., in the rest frame of the pions if there are N pions at time t = 0, there will only be N/2 pions at time t = 1.8 × 10^-8 s. Pions are produced in an accelerator and emerge with a speed of 0.998c. How far do these particles travel in the laboratory before half of them have decayed?