Answer:
Step-by-step explanation:
It depends on whether the 30 cm side is the hypotenuse, or one of the legs.
If the 30 cm side is the hypotenuse, then the third side is √(30^2-10^2) = √800 = 20√2 cm
If the 30 cm side is one of the legs, then the hypotenuse is √(30^2+10^2) = √1,000 = 10√10 cm
