Question

is it possible to make a triangle with sides 3m,3.9m,7m. why?

Answer 1

sum of two sides > third side
3 + 7 > 3.9
10 > 3.9

3.9 + 7 > 3
10.9 > 3

3 + 3.9 < 7
6.9 < 7
as 3 + 3.9 is not greater than 7 so it is not possible to make a triangle

Answer 2

No we cant make a triangle with sides 3m,3.9m,7m.
3+3.9 is not greater than 7m