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36 votes
36 votes
A Triangle with an area of 24 square feet has a side of length 10 feet. If all 3 sides are even integers, what is the perimeter of the triangle?

User Alienhard
by
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1 Answer

19 votes
19 votes

Answer:

24 ft

Explanation:

so, we don't know anything else about the triangle ?

ok, let's see.

the area of a triangle is (a side length) × (the height from that side to the opposite corner) / 2

At = 24 = side × height / 2

48 = side × height = 10 × height

height = 48/10 = 4.8 = 24/5

let's say that the height on our known side splits this side into 2 parts, p and q (p+q = 10).

we can calculate the triangle side on the right hand side of our know side by calling it a and using Pythagoras :

a² = height² + q² = (4.8)² + q² = 23.04 + q²

as all sides have to be even integers, a² has to be an even square number larger than 23.04.

and because p+q = 10, we know q must be smaller than 10, and therefore q² smaller than 100.

the only candidates for a² are therefore 36 and 64 (6² and 8²).

in a similar way this applies to the left hand triangle side b tool.

b² = height² + p² = 23.04 + p²

with the same restrictions and possible solutions as a².

we have the possibilities that a = b = 6 or 8, or a = 6 and b = 8 (or vice versa).

let's rule out a=b :

a=b wound also mean p=q=5

then

a² = 23.04 + 5² = 23.04 + 25 = 48.04, which is not an even square integer. therefore, this assumption is wrong.

so, the only possible solution is a = 6 and b = 8 (or vice versa, but it did not matter which is which, as we only need the perimeter, which would be the same either way).

proof :

36 = 23.04 + 12.96 = 23.04 + q²

=> q = 3.6 ft

64 = 23.04 + 40.96 = 23.04 + p²

=> p = 6.4 ft

p+q = 3.6 + 6.4 = 10 ft

perfect, it fits, this is the correct solution

so, the perimeter of the triangle is

10 + 6 + 8 = 24 ft

User Mohit Tyagi
by
3.3k points
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