Find the greatest number which exactly divides $200$ and $320$.

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?

What is the least value that should be added to $1812$ to make it divisible by $7, 11,$ and $14$?

Find the largest number of four digits exactly divisible by $14, 24, 27$ and $32$.

Three pieces of timber $42 \ m$,$49 \ m$,and $63 \ m$ long have to be divided into planks of the same length. What is the greatest possible length of each plank (in $m$)?

Is it possible to divide $1,000$ into two parts such that their $HCF$ is $15$?