Question

One angle of a right-angled triangle is 70${}^{\circ }$. Find the other acute angle.

• A. ${20}^{\circ }$
• B. ${40}^{\circ }$
• C. ${30}^{\circ }$
• D. ${60}^{\circ }$

Answer 1

The correct option is A ${20}^{\circ }$

We know that, Sum of all the angles in a triangle = 180${}^{\circ }$
Let us consider the acute angle as x .
Hence, $x+{90}^{\circ }+{70}^{\circ }={180}^{\circ }$
$\Rightarrow x+{160}^{\circ }={180}^{\circ }$
$\Rightarrow x={180}^{\circ }–{160}^{\circ }$
$\Rightarrow x={20}^{\circ }$
Therefore, the acute angle is ${20}^{\circ }$.