VolumeBoxes and joined boxes
Find the volume of each box. All lengths are in centimeters.
Volume is the third dimension arriving, and the figure has to show it or a child will multiply two numbers and stop. These free printable worksheets draw the box in oblique projection with all three edges labeled.
If they get stuck

The answer key prints on a separate page.
The composite sheets are the standard's own next sentence rather than a variation someone invented: the volume of a solid made of two non-overlapping prisms is the sum of their volumes. It is the step that turns a formula into a method, so it sits alongside the plain boxes rather than in a separate place.
The two prisms in a composite figure share a depth. That is not a simplification for the drawing's sake — a step that is narrower front-to-back as well as shorter changes two things at once, and the addition is what is being practiced.
Volume of a 10 × 7 × 7 stepped solid