Mark M. answered 04/12/16
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Mathematics Teacher - NCLB Highly Qualified
A = a0(0.5)t/5700
0.35a0 = a0(0.5)t/5700
0.35 = (0.5)t/5700
ln 0.35 = ln [0.5t/5700]
ln 0.35 = (t/5700) ln 0.5
-1.04982212 ≈ (t/5700)(-0.693147181)
-5983.98608 ≈ -0.693147181t
8633.06704 ≈ t
35% remains after approximately 8633 years.