Let's assume there are x boys in the class. Then, the number of girls will be 2x because there are twice as many girls as boys.

The total number of students in the class is x + 2x = 3x.

Now, let's calculate the number of students who have handed over their reports.

The number of boys who have handed over their reports is 45% of x, which is 0.45x.

The number of girls who have handed over their reports is 30% of 2x, which is 0.6x.

So, the total number of students who have handed over their reports is 0.45x + 0.6x = 1.05x.

Therefore, the number of students who have not yet handed over their reports is 3x - 1.05x = 1.95x.

The percentage of students who have not yet handed over their reports is:

(1.95x / 3x) * 100% = 65%

So, 65% of the students have not yet handed over their reports