Answer:
10m.
Explanation:
Since there is no remainder we simply need to find the least common multiple of each of the lengths of Janice and Jasmin's strings until we find a multiple that matches for each. Like so...
2*1 = 2 5*1 = 5
2*2 = 4 5*2 = 10
2*3 = 6
2*4 = 8
2*5 = 10
Finally, we have found the first common multiple which is 10m. That means that the shortest equal length for both Janice's and Jasmin's ribbon is 10m.