In quadrilateral abcd, diagonals ac and bd bisect one another

what statement is used to prove that quadrilateral abcd is parallelogram.

Ineed to know the answer to this algebra question.

Iwill give brainliest. suppose tommy walks from his home at (0, 0) to the mall at (0, 5), and then walks to a movie theater at (6, 5). after leaving the theater tommy walks to the store at (6, 0) before returning home. if each grid square represents one block, how many blocks does he walk?

What is the simplified form of square root of 400 to the 100th power ?