Length of the DNA is 510 angstroms. Find the percentage of cytosine. Assume the number of adenine bases is 30 in that DNA.

Pitch of the DNA is 34 angstroms.
Number of turns in the DNA= 510/34= 15 turns
No. of base pairs per turn = 10bp
No. of base pairs in 15 turns- 15 X10= 150bp
No. of adenine = 30= No. of thymine
Total no. of (A+T) = 30+30= 60
Total no. G+C= 300-60= 240
No. of C= 240/2=120
% C= (120/300) X 100= 40%.