The $HCF$ of $6$ and $20$ is . . . . . . .

Find the $HCF$ of the following pairs of numbers:

$Q.1.$ $30$ and $72$

$Q.2.$ $19$ and $23$

Options:
$A. 6, 1$
$B. 1, 6$
$C. 5, 1$
$D. 1, 5$

The Least Common Multiple $(LCM)$ of $6$ and $20$ is . . . . . . .

$\text{l.c.m.} (36, 94) = \dots$

Four bells toll at intervals of $8$,$12$,$15$,and $18$ seconds respectively. All four begin to toll together. How many times will they toll together in one hour,excluding the one at the start?

$A$ 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?