Jacinta is working on a jigsaw puzzle that has 403 pieces. she has completed 1/4 of the puzzle. about how many pieces has she placed in the puzzle

 
to get any fraction of a number, as long as the numerator is 1 in the fraction, just divide by the denominator. In this case it's 4. Since you can't place .75 of a puzzle piece, she's placed 100 pieces in the puzzle.