What is the $H.C.F.$ of $27, 18$ and $36$?

The $H.C.F.$ of two numbers is $12$ and their difference is $12$. The numbers are:

There are five bells which start ringing together at intervals of $3, 6, 9, 12$ and $15$ seconds respectively. In $36$ minutes,how many times will the bells ring simultaneously?

Find the greatest number of four digits which is exactly divisible by $24, 28, 30$ and $35$.

Find the sum of the numbers between $500$ and $700$ such that when they are divided by $6, 8$ and $12$ it leaves no remainder.

Given: $\sqrt[3]{4}, \sqrt{3}, \sqrt[6]{25}$ and $\sqrt[12]{289},$ the greatest and least of them are respectively