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 $m$)?

Find the greatest number of five digits which becomes exactly divisible by $10, 12, 15$ and $18$ when $3769$ is added to it.

Find the side of the largest square slab which can be paved on the floor of a room $5 \, m \, 44 \, cm$ long and $3 \, m \, 74 \, cm$ broad.

The smallest number which when diminished by $7,$ is divisible by $12, 16, 18, 21$ and $28$ is

Let $N$ be the least six-digit number which,when divided by $4, 6, 10,$ and $15,$ leaves the same remainder of $2$ in each case. The sum of the digits in $N$ is:

Seema,Meena,and Reena start jogging around a circular stadium and complete one round in $54 \text{ seconds}$,$42 \text{ seconds}$,and $63 \text{ seconds}$ respectively. Approximately after how many minutes will they meet again at the starting point?