In a laboratory, two bottles contain mixture of acid and water in the ratio 2 : 5 in the first bottle and 7 : 3 in the second. The ratio in which the contents of these two bottles be mixed such that the new mixture has acid and water in the ratio 2:3 is

ratio of acid and water in the first bottle = 2 : 5

acid in the first bottle = $$ \frac{2}{7} $$

ratio of acid and water in the second bottle = 7 : 3

acid in the second bottle = $$ \frac{7}{10} $$

ratio of acid and water in the new mixture = 2 : 3

acid of new mixture = $$ \frac{2}{5} $$

using alligation method

ratio in which the contents of these two bottles be mixed = $$ \frac{3}{10} : \frac{4}{35} $$

                                                                                        = 21 : 8