The $HCF$ of $13$,$23$,and $31$ is . . . . . . .

Find the $HCF$ of $12, 15$,and $21$.

$A$ sweetseller has $420$ kaju barfis and $130$ badam barfis. She wants to stack them in such a way that each stack has the same number,and they take up the least area of the tray. What is the number of barfis that can be placed in each stack for this purpose?

The smallest positive number divisible by $24, 36$,and $48$ is $\ldots \ldots \ldots \ldots .$

Find the $\text{g.c.d.}$ (Greatest Common Divisor) of $196$ and $38220$ using Euclid's division algorithm.

State whether the following rational number has a terminating decimal expansion or not. If it has a terminating decimal expansion,find it: $\frac{35}{50}$