Math Mania 2009

  1. Gizmos cost $3 each and doodads cost $4 each. If you buy a total of 20 gizmos and doodads for $75, how many doodads did you buy?
  2. If the radius of a sphere is increased by 20%, by what percentage does the surface area of the sphere increase?
  3. In the triangle shown, segments AB, BD, and CD are congruent. What is the measure of angle ABC?
    triangle with a line down the middle. triangle points are labeled a, b and c. where the middle line meets the base of the triangle is labeled d.
  4. What’s the next most likely term in the sequence 1, 5, 15, 34, 65, 111, …?
  5. Five people forget their backpacks in class. Their teacher returns the backpacks randomly. What is the probability that exactly two of them get their own backpacks?

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