6th grade triangles with a missing side worksheets

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Triangles with a missing side worksheets for 6th grade print 6 problems per page. Find each area or missing length. Show your calculation. Triangle area is half the product of base and perpendicular height. The height may meet an extension of the base.

Free printable PDF worksheet, aligned to Common Core 6.G.A.1.

Each print is a different sheet with its own answer key. You don't need to sign up.

The kind of problems you'll get

Find each area or missing length. Show your calculation.

  1. Base: 8 cm; perpendicular height: 3 cm.

    Answer: (8 × 3) ÷ 2 = 12 cm².

Most problems on this sheet sit beside a picture, model or diagram, so this is the worked example the sheet itself prints. The answer key on page two prints the answer under every problem.

Every print pulls a fresh set of problems at this level, so a make-up test or a second sibling never gets the same sheet.

What's on each sheet

Every version prints on US Letter or A4, with its answer key after the problems.

This sheet is one of the versions on the 6th grade area of triangles page, with its own difficulty choices and its own answer key.

How to teach this

The half is the whole lesson, so make it visible once: draw a rectangle, slice it corner to corner, and shade one triangle: half the box, every time. Then let your child choose the order that feels safer, multiplying first and halving at the end, or halving one number first when it's even. If answers keep coming out doubled, the half got skipped; that's the first place to look.

Watch for: Kids forget the half and double every answer. A triangle is half the parallelogram with the same base and height, so divide by 2 at the end. Kids use a slanted side as the height. The height is the dashed line that meets the base at a right angle.

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Aligned to Common Core 6.G.A.1. Reviewed by the One more sheet team. Content version 241, updated September 2026.

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