Simplify $\left( \tfrac{3}{4}\text{ of }\tfrac{4}{9}\div 9\tfrac{1}{2} \right)\div 1\tfrac{5}{19}$

A student spent $\tfrac{1}{5}$of his allowance on books, $\tfrac{1}{3}$of the reminder on food and kept the rest for contingencies. What fraction was kept.

Evaluate $\frac{81.81+99.44}{20.09+36.16}$

Simplify $7\tfrac{1}{12}-4\tfrac{3}{4}+2\tfrac{1}{2}$

Evaluate $\frac{\tfrac{3}{8}\div \tfrac{1}{2}-\tfrac{1}{3}}{\tfrac{1}{8}\times \tfrac{2}{3}+\tfrac{1}{3}}$

Simplify $\tfrac{3}{5}\div (\tfrac{2}{7}\times \tfrac{4}{3}\div \tfrac{4}{9})$

Simplify $\left( \tfrac{7}{9}-\tfrac{2}{3} \right)\div \left( \tfrac{1}{3}+\tfrac{2}{5}\div \tfrac{4}{5} \right)$

If $m:n=13:11$find $({{m}^{2}}-{{n}^{2}}):{{(m+n)}^{2}}$

Simplify $3\tfrac{1}{2}-(2\tfrac{1}{3}\times 1\tfrac{1}{4})+\tfrac{3}{5}$

A farmer planted 5000 grains of maize and harvested 5000cobs, each bearing 500 grains. What is the ratio of the number of grains sowed to the number harvested?