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.)
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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Tags: Jenny, Jigsaw Puzzle, Little Brother
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
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