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  • Lighthouse on the Coast

     Vivek updated 1 year, 2 months ago 2 Members · 2 Posts
  • Puzzle Prime

    November 13, 2020 at 2:52 pm

    A lighthouse is x miles away from the coast. Its beam makes 1 revolution per minute. How fast is the beam moving along the beach, when the point on the beach it lightens up is y miles away from the point on the beach closest to the lighthouse?

  • Vivek

    November 17, 2020 at 12:33 pm

    The distance from the base of the lighthouse to the light beam is not going to change as it revolves and it is sqrt(x^2+y^2). So The speed is 2*pi*sqrt(x^2+y^2) per minute.

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