Answer:
The other leg is 4 m long, and the hypotenuse is 5 m long
Step-by-step explanation:
Recall that the longest side of a right angle triangle is its hypotenuse, and that the legs and hypotenuse must verify the Pythagorean identity:

so, we know that the other two sides have consecutive integers for lengths. That is: if one is "x" in length, the other one must be "x+1"
So we can assume that the largest of this is the hypotenuse: "x+1"
Not, they must verify the Pythagorean identity:

then, the other side is of length 4 m, and finally the hypotenuse is of length 4+1 = 5 m