Consider a stream of n cash flows. Let CF; denote the dollar value of the ith cash flow, let ti the time (in years) at which it will be received and let PV(r) denote the present value of the stream given that all cash flows are discounted at the continuously compounded rate r. Prove that the duration of the stream is PV'(r)/PV(r). Consider a stream of n cash flows. Let CF; denote the dollar value of the ith cash flow, let ti the time (in years) at which it will be received and let PV(r) denote the present value of the stream given that all cash flows are discounted at the continuously compounded rate r. Prove that the duration of the stream is PV'(r)/PV(r)