question: Sarah has a rope that is 20 meters long. Her friend wants to buy the rope for $2 a meter. Sarah plans to use the profit to buy a new rope, which at the store costs $1.5 a meter. How much money will she have left over after she buys the new rope?
answer: Her friend pays her $40 for the rope because 20 x 2 = <<20*2=40>>40
  She can buy the rope at the store for $30 because 20 x 1.5 = <<20*1.5=30>>30
  She has $10 left over because 40 - 30 = <<40-30=10>>10
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