Multiple choice

On a sunny day, a tower casts its shadow across a field. At 10:00 AM, the shadow of the tower reaches point P. By 4:00 PM, the shadow stretches to point Q. and the distance between P and Q 14 measures 80 meters. During this time, the angle of the sun's elevation changes from 60 degrees to 30 degrees, then determine the height of the tower?

  1. 20 3 m

  2. 15 3 m

  3. 18 3 m

  4. 25 3 m

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A Correct answer
AI explanation

Let the height of the tower be h and the distance from its base to point Q be x, so tan 30 degrees equals h divided by (x + 80) and tan 60 degrees equals h divided by x. This gives x equals h divided by root 3 and x + 80 equals root 3 times h. Substituting the first into the second yields h divided by root 3 + 80 equals root 3 times h, which simplifies to 80 equals 2h divided by root 3, making the height 40 divided by root 3, or 20 root 3 meters.