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1983 AMC 12 Question 27

AMC12 · 1983 AMC 12

Question 27

A large sphere is on a horizontal field on a sunny day. At a certain time the shadow of the sphere reaches out a distance of $10$ m from the point where the sphere touches the ground. At the same instant a meter stick (held vertically with one end on the ground) casts a shadow of length $2$ m. What is the radius of the sphere in meters? (Assume the sun’s rays are parallel and the meter stick is a line segment.)
  1. $\frac52$
  2. $9-4\sqrt5$
  3. $8\sqrt{10}-23$
  4. $6-\sqrt{15}$
  5. $10\sqrt5-20$