MATH SOLVE

3 months ago

Q:
# Jenny has just started working on a 250 piece jigsaw puzzle. 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.)

Accepted Solution

A:

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

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