How to read 57 mm on a constructed scale with decimeter and centimeter markings?

Since $1 \text{ dm} = 10 \text{ cm}$ and $1 \text{ cm} = 10 \text{ mm}$:

So, you need to measure 0 dm, 5 cm, and 7 mm.

Since 57 mm is less than 1 dm, you will use the leftmost section of the scale, which is designed for reading centimeters. The decimeter reading is '0'.

Start at the '0' mark on your scale (this is the point where the decimeter scale begins and the centimeter scale ends).
Move to the left along the centimeter subdivisions. Each small division represents 1 cm.
Count 5 of these small divisions to the left from the '0' mark. This point represents 5 cm.

The remaining 7 mm (or 0.7 cm) cannot be read precisely on this scale because the smallest divisions represent 1 cm.
To represent 57 mm, you would locate the 5 cm mark (as described in Step 3) and then visually estimate 7 tenths of the distance to the next centimeter mark (which would be the 6 cm mark).

Therefore, to read 57 mm, you would measure the length from the '0' mark on the right, extending left to the 5 cm mark, and then visually estimate an additional 7 mm within the next 1 cm division.