NMTC Practice Part 6

Geometry Level 1

Two sides of a triangle are 10 10 and 5 5 units in length, and the length of the median to the third side is 6.5 6.5 units. The area of the triangle is 6 x 6\sqrt{x} units squared. Determine the value of x x .


This question has appeared in NMTC.


The answer is 14.

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3 solutions

Rifath Rahman
Aug 20, 2014

By using Apollonius Theorem we get the half the third side 4.5,then the side is 9,By using Heron's law we get area 6 * sqrt 14.So x=14

same way!!!

Kartik Sharma - 6 years, 9 months ago

I derived a formula for median and then used that formula to solve.

Kushagra Sahni - 6 years, 9 months ago

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Yes, the formula for median can be derived by stewart's theorem

Bala vidyadharan - 5 years, 9 months ago

Median of any triangle = 1 2 2 A B 2 + 2 A C 2 B C 2 =\dfrac{1}{2}\sqrt{2AB^2+2AC^2-BC^2}
Let median be A M AM .
A M = 1 2 2 A B 2 + 2 A C 2 B C 2 \Rightarrow AM =\dfrac{1}{2}\sqrt{2AB^2+2AC^2-BC^2}
13 = 2 A B 2 + 2 A C 2 B C 2 \Rightarrow 13=\sqrt{2AB^2+2AC^2-BC^2}
B C = 9 \Rightarrow BC=\boxed{9}



Now, by Heron's formula.

s ( s a ) ( s b ) ( s c ) \Rightarrow \sqrt{s(s-a)(s-b)(s-c)}
s = 10 + 5 + 9 2 = 24 s=\dfrac{10+5+9}{2}=24

12 × 2 × 7 × 3 \Rightarrow \sqrt{12×2×7×3}
6 14 = 6 x \Rightarrow 6\sqrt{14}=6\sqrt{x}
x = 14 \therefore x=\boxed{14}

Basically we just simply need to use Apollonius theorem and then use Heron's Formula for the area, I solved it using this method

Tisya Rawat - 4 months, 4 weeks ago

Appollonius ,then use herons you will get the answer

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