A square postage stamp has area 1,250 mm^2. About how long is each​ side?

To find the length of each side of the square postage stamp, we need to take the square root of the area.

So, the length of each side is the square root of 1,250 mm^2:

length of each side = √1,250 mm^2
length of each side ≈ 35.36 mm

Therefore, each side of the square postage stamp is approximately 35.36 mm.