Answer:
2 movements
Step-by-step explanation:
In this case what we will do is name the white chips "W" and the black ones "B". If there are 9 tiles and 4 are in black then the rest, that is 5, in white, like this:
B-B-B-B-W-W-W-W-W
First movement, in turn we can flip 3 tiles, in this case we flip two blacks and one white, it would look like this:
W-W-B-B-B-W-W-W-W
The second movement is to turn the 3 black ones and thus they would all be blank
W-W-W-W-W-W-W-W-W
In other words, the smallest number of movements is 2.