The formula of the present value of annuity ordinary is
Pv=pmt [(1-(1+r/k)^(-kn))÷(r/k)]
Pv present value 1200000
PMT semiannual payment 75000
R interest rate 0.0635
K compounded semiannual 2
N time?
1200000=75000[(1-(1+0.0635/2)^(-2n))÷(0.0635/2)]
Solve for n
1,200,000÷75,000=[(1-(1+0.0635/2)^(-2n))÷(0.0635/2)]
16=[(1-(1+0.0635/2)^(-2n))÷(0.0635/2)]
16×(0.0635÷2)=(1-(1+0.0635/2)^(-2n))
0.508=(1-(1+0.0635/2)^(-2n))
0.508−1=-(1+0.0635/2)^(-2n)
−0.492=-(1+0.0635/2)^(-2n)
0.492=(1+0.0635/2)^(-2n)
-2n=log(0.492)÷log(1+0.0635÷2)
N=-[log(0.492)÷log(1+0.0635÷2)]÷2
N=11.35 years