$\frac{\frac{1}{2} \div 4 + 20}{\frac{1}{2} \times 4 + 20} = ?$

The value of $\frac{1}{1 \times 2} + \frac{1}{2 \times 3} + \frac{1}{3 \times 4} + \ldots + \frac{1}{9 \times 10}$ is

$A$ pineapple costs $Rs. 7$ each. $A$ watermelon costs $Rs. 5$ each. $X$ spends $Rs. 38$ on these fruits. The number of watermelons purchased is

If $\sqrt{2^{n}} = 64$,then find the value of $n$.

$A$ man has some hens and cows. If the number of heads is $48$ and the number of legs is $140$,then the number of hens is:

The value of $\frac{1}{a^{2}+a x+x^{2}}-\frac{1}{a^{2}-a x+x^{2}}+\frac{2 a x}{a^{4}+a^{2} x^{2}+x^{4}}$ is