Question

(100pts.) A triangle has all integer side lengths and two of those sides have lengths 9 and 16. Consider the altitudes to the three sides. What is the largest possible value of the ratio of any two of those altitudes?
Improper answers will be reported

Answer 1

Answer:

  8/3

Step-by-step explanation:

The range of possible lengths for the third side is 16±9, or 7 to 25. For lengths of 7 and 25, the area of the triangle will be zero, so the ratio of altitudes will be infinite (actually, undefined, as division by 0 is involved).

For positive triangle area and integer side lengths, the range of side lengths can be from 8 to 24. For any given triangle, the ratio of maximum altitude to minimum altitude will be the same as the ratio of the maximum side length to the minimum side length.

For the triangles under consideration, the shortest side length we can have is 8. For that 8-9-16 triangle, the ratio of the maximum to minimum side lengths is 16/8 = 2.

The longest side length we can have is 24. For that 9-16-24 triangle, the ratio of maximum to minimum side lengths is 24/9 = 8/3 = 2 2/3. This is more than 2, so 8/3 is the largest possible ratio of any two altitudes.

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More explanation

The area of a triangle is given by the formula ...

  A = (1/2)bh

Then the altitude for a given base (b) is ...

  h = 2A/b

That is, the altitude is inversely proportional to the base length for a triangle of a given area. Once you choose the three sides of the triangle, the area is fixed, so the ratio of altitudes is the inverse of the ratio of base lengths. The ratio of maximum altitude to minimum altitude is the ratio of the inverse of the minimum base length to the inverse of the maximum base length, which is to say it is the same as the ratio of maximum to minimum base lengths.