Josue asked:


She usually takes 3 hours to work a puzzle of that size. Her little brother wants to help. He could put the puzzle together in 6 hours. How much time would the two need to work the puzzle together? (Round your answer to the nearest tenth.)

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2 Comments to “Jenny has just started working on a 250 piece jigsaw puzzle?”

  1. Phil D says:

    You need to figure out the rates at which they both work.

    For Jenny, its 250 pieces / 3 hours = 83.3 pieces / hour
    For her brother, its 250 pieces / 6 hours = 41.7 pieces / hour

    so together, that adds up to 125 pieces / hour.

    (125 pieces / hour) = (1/125) hours / piece
    (1/125) hours / piece * 250 pieces = 2 hours because the pieces on the top and bottom cancel

    so the answer is 2 hours

  2. manjyomesando1 says:

    1/(Jenny’s time) + 1/(brother’s time) = 1/(time working together)
    1/3 + 1/6 = (2 + 1)/6 = 3/6 = 1/2

    answer = 2 hours

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