So hmm notice the picture below
running a segment from the right-angle perpendicular to the opposite side, gives three similar triangles, one small, a medium and a large one
now, using proportions, you can simply

and solve for "x"
It would take 17 months because 1000 x .3 = 30. 30 x 17 is 510. but if you were trying to get the exact number it would be 16 months and 10 days.
7 tables minimum in order to seat 33 kids