# 9th Grade Easy Triangle Question For Most

• Dec 9th 2009, 06:32 PM
4woods
9th Grade Easy Triangle Question For Most
The three angles of a triangle have measures 12x degrees, 3x degrees, and 7y degrees, where 7y is greater than 60. If x and y are integers, what is the value of X?
• Dec 9th 2009, 06:36 PM
mr fantastic
Quote:

Originally Posted by 4woods
The three angles of a triangle have measures 12x degrees, 3x degrees, and 7y degrees, where 7y is greater than 60. If x and y are integers, what is the value of X?

Solve 15x + 7y = 180, where 7y > 60 and x and y are whole numbers, by trial and errror.

eg. y = 9 => 7y = 63 satisfies the first condition. But 15x = 180 - 63 = 117 does not have a solution for x that's a whole number. So try again ....
• Dec 9th 2009, 06:54 PM
Soroban
Hello, 4woods!

Quote:

The three angles of a triangle have measures $\displaystyle 12x$ degrees, $\displaystyle 3x$ degrees,
and $\displaystyle 7y$ degrees, where $\displaystyle {\color{red}\rlap{///////}}7y > 60$ .
Unnecessary and confusing . . .

If $\displaystyle x$ and $\displaystyle y$ are integers, what is the value of $\displaystyle x$ ?

The three angles of a triangle always total 180°.

Hence: .$\displaystyle 12x + 3x + 7y \:=\:180 \quad\Rightarrow\quad x \:=\:\frac{180-7y}{15} \:=\:12 - \frac{7y}{15}$

Since $\displaystyle x$ is an integer, $\displaystyle y$ must be a multiple of 15.

$\displaystyle \text{Since }7y < 180\text{, then }\,y < 26.\;\;\text{ Hence: }\:y = 15$.

Therefore: .$\displaystyle x \;=\;12 - \frac{7(15)}{15} \quad\Rightarrow\quad \boxed{x \:=\:5}$