Correct Answer - Option 4 : 6 ∶ 7 ∶ 8

**Concept:**

Sum of interior angle of triangle = 180°

**Calculation:**

1)1 : 2 : 3

So, x + 2x + 3x = 6x

Then 6x = 180°, x = 30°

Angles 30°, 60° and 90°

2) 3 : 4 : 5

So, 3x + 4x + 5x = 180°

Then 12x = 180°, x = 15

Angles 45°, 60° and 75°

3) 5 : 6 : 7

So, 5x + 6x + 7x = 180°

Then 18x = 180°, x = 10°

Angles 50°, 60° and 70°

4) 6 : 7 : 8

So, 6x + 7x + 8x = 180°

Then 21x = 180°, x = 8.57°

Angles 51.42°, 59.99° and 68.57°

**∴ Option 4 is not integar angle in triangle**.