Multiple choice

If John makes a contribution to a charity fund at school, the average contribution size will increase by 50%, reaching $75 per person. If there were 5 other contributions made before John`s, what is the size of his donation?

  1. $100
  2. $150
  3. $200
  4. $250
  5. $450
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let the sum of the 5 previous contributions be S. The original average was S/5. The new average is (S + x) / 6 = 75, so S + x = 450. The new average is 1.5 * (S/5), so (S + x) / 6 = 1.5 * (S/5). Substituting S + x = 450: 450 / 6 = 75 = 1.5 * (S/5), so S/5 = 50, S = 250. Then x = 450 - 250 = 200.

AI explanation

Since the new average contribution is \$75, which represents a 150% increase from the original average, the initial average was \$50. The total contribution for the 5 original people was 5 multiplied by $50, equaling $250. With John included, the total contribution for 6 people becomes 6 multiplied by $75, equaling $450. John's donation is the difference between the new total and the old total, so $450 minus $250 equals $200.

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