P6 Work backwards from volume or area
Cuboid face area — volume 384 cm³
A cuboid has volume 384 cm³ and depth 8 cm. Find the area of the face perpendicular to that depth.
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The pattern behind it: Work backwards from volume or area
Use the known area or volume to find the missing measurement.
In this one. Use the dimension perpendicular to the chosen face. Volume divided by that dimension gives the face area, not a side length.
How to spot it
The question gives a cuboid's volume with two dimensions and asks for the third, or gives the volume with one length and asks for a face area. A square's area given with its side asked for belongs here too.
Common mistake
Children divide the volume by a length lying inside the face they want, instead of the length that runs into it, and get the wrong kind of measurement.
Try one like it
Standard A square with area 100 cm² A square has area 100 cm². Write its side length using square-root notation, then evaluate it.The 33 problem patterns
All 33 patterns, one to a page — the 19 behind Primary 5 and 6 word problems, and the skills the younger years are built on. The bar model, how to spot it in the question, and the mistake children make. A booklet you can print. Free.
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