The Triangles and Its Properties — MATHS STD 7 — Question
Gujarat BoardEnglish MediumSTD 7MATHSThe Triangles and Its Properties3 Marks
Question
Find the value of the unknown interior angle $x$ in the figure:
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Answer
Given that,
$1^{\text {st }}$ interior angle $=70^{\circ}$ and $2^{\text {nd }}$ interior angle $=x$
Now, According to exterior angle theorem:
The measure of an exterior angle of a triangle is equal to the sum of the measure of the two non-adjacent interior angles of the triangle.
Here, Exterior angle $=100^{\circ}$
Sum of interior angles $=70^{\circ}+x$
Using exterior angle theorem, we have
$100^{\circ}=70^{\circ}+x$
$x=100^{\circ}-70^{\circ}$
$x=30^{\circ}$
Hence, the value of $x$ is $30^{\circ}$
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