#9 . . . #12, and #14: Excellent. All correct, and good estimates.
#13: A very picky comment: Your math is correct, but the camera can't take 2/3 of an image. That's why the question asked "How many complete images ...". After 66 images, there is still some time remaining, but not enough for another image. So it captures 66 complete images in 3 seconds.
If you are really in elementary school, then I think you're doing the work of a prodigy. Keep it up ! And best of luck to you.
The formula for finding the circumference is pi times the diameter so If your giving it in terms of pi then you're just finding the diameter which is 15
