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 the number of bushes in the beginning was 

(a) 25000 

(b) 27000 

(c) 28000 

(d) 24600

Answer 1

(a) 25000

Let the number of bushes in the beginning be x

Then, 26730 = x\(\big(1+\frac{10}{100}\big)\)\(\big(1+\frac{8}{100}\big)\)\(\big(1-\frac{10}{100}\big)\)

\(\Rightarrow\)26730 = x x \(\frac{11}{10}\) x \(\frac{27}{25}\) x \(\frac{9}{10}\)

\(\Rightarrow\) x = \(\frac{26730\times 10\times 25 \times10}{11\times9\times27}\)

\(\Rightarrow\)x = 25000.