Math Is Fun Forum

Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫  π  -¹ ² ³ °

You are not logged in.

#1 2021-05-26 16:49:33

mctoosh0
Member
Registered: 2021-05-26
Posts: 1

Lengthy Relationship Puzzle - is the solution posted correct?

a triangle is show with side lengths 3, 5 and 8. The length 8 is bisected and an unknown length x connects this midpoint and the vertex of the 2 other sides. The solution contends the unknown length is 1.

How can this be? Can you have a triangle if the total length of 2 sides is NOT longer than the 3rd? - No.

The solution must be x=0. intuition also says it must be zero.

Let's use algebra to solve. Construct a line from the vertex of lines 5 &3 perpendicular to the side length 8. call this unknown length b. The distance between the mid-point of the length 8 and the perpendicular line is unknown. call this length a.

using pythagoras. 1. b^2+(4-a)^2=3^2 & 2. b^2+(4+a)^2=5^2.
substitute b^2 from 1 into 2. Solve for 1. a=1
substitute a=1 and equations 1 & 2 give you b = 0. If b=0 then x=0

Offline

#2 2021-05-26 20:18:35

Bob Registered: 2010-06-20
Posts: 9,355

Re: Lengthy Relationship Puzzle - is the solution posted correct?

hi mctoosh0

Welcome to the forum.

That proof looks good to me. Well done!

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob Offline