What is the distance between two successive nitrogen base pairs in a $DNA$ double helix?

What is the length of one full turn of the helix in $\beta-DNA$ (in $, nm$)?

If the distance between two consecutive base pairs in a $DNA$ molecule is $0.34 \ nm$ and the total number of base pairs in a typical mammalian cell is $6.6 \times 10^9 \ bp$,what is the approximate length of the $DNA$ (in $m$)?

Which of the following is $NOT$ true for the double-helical structure of $DNA$?

If the percentage of thymine in $DNA$ is $20\%$,what will be the percentage of guanine (in $\%$)?

What is the function of histones in $DNA$ packaging?