Multiple choice

Five friends purchased some books from a book shop. Four of them purchased books worth \$30 each. If the fifth one purchased books worth \$40 more than the average of all of them together, what was the total cost of the books purchased by all?

  1. $140
  2. $160
  3. $180
  4. $200
  5. $220
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D Correct answer
Explanation

Let the total cost be T. Average = T/5. The fifth person paid 30 + 30 + 30 + 30 + (T/5 + 40) = T. 120 + T/5 + 40 = T. 160 = 4T/5. T = 160 * 5 / 4 = 200.

AI explanation

Let the average cost be x, making the fifth person's cost (x + 40). The total cost is 4 times 30 plus (x + 40), which equals 5x. Solving 120 + x + 40 = 5x gives 4x = 160, so x = 40. The total cost is 5x, which is 200.

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