Answer
The magnitude is $\sqrt 125$.
Work Step by Step
The magnitudes of vectors (a) and (b) respectively are 5m, and 10m. The vectors create a triangle with one missing side. That missing side is the magnitude of (a) + (b). Use Pythagorean's Theorem to find the missing side.--- $5^{2}$ + $10^{2}$ = $\sqrt 125$
(11.18m)
