Step-by-step explanation:
this is an isoceles, right-angled triangle.
but legs are equally long (6 m), and the baseline is per Pythagoras
baseline² = leg1² + leg2² = 6² + 6² = 36 + 36 = 72
baseline = sqrt(72) = 8.485281374... m
so, the perimeter is
6 + 6 + 8.485281374... = 20.485281374... ≈ 20.5 m
so, B is the right answer.
