Question

Identify the option for which a triangle can't be formed by combining all the sides or angles present in the option.

• A. 45°, 65° and 70°
• B. 3 units, 4 units and 5 units
• C. 3 units, 4 units and 7 units
• D. 45°, 45° and 90°

Answer 1

The correct option is C 3 units, 4 units and 7 units

Option 'a':

The angles given are 45°, 65°, and 70°.

The sum of interior angles of a triangle should be equal to 180°. More than 1 triangle can be formed as different triangles can increase the sides.

So, 45° + 65° + 70° = 180°
∴ Option 'a' is correct.

Option 'b':

The side length of the triangle is 3 units, 4 units, and 5 units.

Using the triangle inequality theorem, we can say that the sum of any two sides of the triangle should be greater than the third side of the triangle.

3 + 4 > 5

4 + 5 > 3

3 + 5 > 4

So, the three sides form a unique triangle.
∴ Option 'b' is correct.

Option 'c':

The side length of the triangle is 3 units, 4 units, and 7 units.

3 + 4 = 7

So, no triangle formation is possible with side lengths as 3 units, 4 units, and 7 units.
∴ Option 'c' is incorrect.

Option 'd':

The angles given are 45°, 45°, and 90°.

45° + 45° + 90° = 180°.

∴ Option 'd' is correct.

So, the only incorrect option is
option 'c'.