Write about which method you prefer to use to divide by 5 counting up, counting back on a number line, or dividing by 10, and then doubling the quotient?

In First method : counting up, counting back on a number line,

If we want the quotient after dividing the number by 5 then we count how many 5 we get from 0 to the dividend.

For example :  

Since, from 0 to 30 there are six 5's obtained. ( because 5 × 6 = 30 )

Thus,  

In Second Method : dividing by 10, and then doubling the quotient.

First we divide the number by 10 then multiply the quotient by 2.

For Example:

Since,

Thus,

Now, when we compare the above methods then we conclude that for the smaller numbers first method is appropriate because for small numbers we can easily count total 5's from 0. While for large numbers Second method is appropriate because it is hard to count the total 5's for the large number.