Question

3. Angles of a triangle are in ratio of 1:5:12,
biggest angle of this triangle is
(A) 450
(B) 120°
90°
(D) 60°​

Answer 1

Let angles be 1x , 5x and 12x
1x + 5x + 12x = 180 (Angle Sum property of Δ)
18x = 180
x = 10
So, 1x = 1*10 = 10°
5x= 5*10 = 50°
12x = 12*10= 120°
The biggest angle of this triangle = 120°
so, option (B) is correct

Answer 2

Answer:

Option (B) 120°

Step-by-step explanation:

Given that,

Ratio of angles = 1:5:12

To find,

The biggest angle = ?

Assumption,

Let angles be represented as x.

We know that,

Sum of all the angles of a triangle = 180°

So,

x + 5x + 12x = 180°

18x = 180°

x = $\frac{180°}{18}$

x = $\frac{\cancel{180°}}{\cancel{18}}$

x = 10°

Substituting x = 10 in x, 5x and 12x, we obtain,

Angle one: x = 10°

Angle two: 5x = 5(10) = 50°

Angle three: 12x = 12(10) = 120°

Therefore, we can say that,

Angle one < Angle two < Angle three

Therefore, 10° < 50° < 120°

Therefore, 120° is the largest angle.

Therefore, option (B) 120° is correct.