# Tick the correct answer and justify : In ∆ABC, AB = 6√3 cm, AC = 12 cm and BC = 6 cm. The angle B is :

(A) 120° (B) 60° (C) 90° (D) 45°

**Solution:**

In a triangle, if square of one side is equal to the sum of the squares of the other two sides, then the angle opposite the first side is a right angle. [Pythagoras theorem]

(c)

In ΔABC

AB = 6√3 cm; AC = 12 cm; BC = 6 cm

AB^{2} = 108 cm^{2}; AC^{2} = 144 cm^{2}; BC^{2} = 36 cm^{2}

AB^{2} + BC^{2} = (108 + 36) cm^{2}

= 144 cm^{2}

⇒ AC^{2} = AB^{2} +BC^{2}

Pythagoras theorem satisfied

⇒ ∠ABC = 90°

Thus, option (C) 90° is the correct answer.

**Video Solution:**

## Tick the correct answer and justify : In ∆ABC, AB = 6√3 cm, AC = 12 cm and BC = 6 cm. The angle B is : (A) 120° (B) 60° (C) 90° (D) 45°

### NCERT Class 10 Maths Solutions - Chapter 6 Exercise 6.5 Question 17:

Tick the correct answer and justify : In ∆ABC, AB = 6√3 cm, AC = 12 cm and BC = 6 cm. The angle B is : (A) 120° (B) 60° (C) 90° (D) 45°

For the given triangle In ∆ABC, AB = 63 cm, AC = 12 cm and BC = 6 cm. The angle B is 90 degrees.