
Let △ABC and △DEF are two similar triangles such that ar (△ABC) =100cm2 and ar (△DEF) = 64cm2
Also, let AM and DN are medians of △ABC and △DEF respectively.
Now in △ABC and △DEF
∠B = ∠E [∵△ABC ~ △DEF]

We know that, the ratio of two similar triangles is equal to the square of the ratio of their corresponding sides.

Hence, the length of the other median is 7cm.