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$$\left.47\,000\cdot\left(1+\frac{4}{100}\right)^n=93\,000\quad\right|\;:47\,000$$$$\left.\left(1+\frac{4}{100}\right)^n=\frac{93}{47}\quad\right|\;\ln(\cdots)$$$$\left.n\cdot\ln\left(1+\frac{4}{100}\right)=\ln\left(\frac{93}{47}\right)\quad\right|\;:\ln\left(1+\frac{p}{100}\right)$$$$\left.n=\frac{\ln\left(\frac{93}{47}\right)}{\ln\left(1+\frac{4}{100}\right)}\quad\right.$$$$n=17,400$$