The lengths of two sides of a triangle are 20 mm and 15 mm. Which of these lengths cannot represent the length of the third side.

✓
40

×
30

×
20

×
15
The lengths of two sides of a triangle are 20 mm and 15 mm. Which of these lengths cannot represent the length of the third side.
40
30
20
15
\because 40 > 20 + 15 = 35
\therefore 40 is not the third side of the triangle
\because 30 < 20 + 15 = 35
\therefore 30 is the third side of the triangle
\because 20 < 20 + 15 = 35
\therefore 20 is the third side of the triangle
\because 15 < 20 + 15 = 35
\therefore 10 is the third side of the triangle