3. Out of 10 million muons detected at an altitude of 10 km above the surface of the earth, how many will reach the ground? (Vmuon = .98c; half-life* = 1.56 x 10-6 s). * after one half-life, we'd expect half as many muons as we started with, so 5 million, and then after another half-life, half again, so 2.5 million and so on