Question

The population of a variety of tiny bush in an experimental field increased by 10% in the first year, increased by 8% in the second year but decreased by 10 in the third year. If the present number of bushes in the experimental field is 26730, then find the number of bushes in the beginning.

Answer 1

Let the number of bushes in the beginning is P so
$P\times (1+\frac{10}{100})(1+\frac{8}{100})(1-\frac{10}{100})=26730$
$\Rightarrow$ P = $\frac{26730}{(1+\frac{10}{100})(1+\frac{8}{100})(1-\frac{10}{100})}\Rightarrow P=(26730\times \frac{10}{11}\times \frac{25}{27}\times \frac{10}{9})\Rightarrow P=25000$