Geometric diagram conventions · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Reading marks in a geometry diagram

Mathematics · Geometry · ages 9-12
Name ______________________   Date ____________

  1. In a geometry diagram, what does a small square drawn in the corner where two lines meet tell you?

    • The angle there is a right angle, 90 degrees
    • The two lines are the same length
    • The angle is smaller than 90 degrees
    • The two lines never cross

  2. In a diagram, a small square is drawn in the corner between two lines. What angle is that?

    • A right angle (90°)
    • A wide angle (more than 90°)
    • An angle that hasn't been measured yet

  3. Angle ABC has its vertex, or corner point, at B.

    Circle one:   True   False

  4. A diagram shows two sides of a shape, each with a single tick mark. What does that tell you?

    • The two sides are equal in length
    • The two sides are parallel
    • The two sides meet at a right angle

  5. If a quadrilateral has one tick mark on each of its four sides, that by itself proves it is a square.

    Circle one:   True   False

  6. Maya wants to use exactly five diagram markings to show that a quadrilateral is a square. Which plan can work?

    • Put one tick mark on each of the four sides, and draw one small square in a corner
    • Draw small squares in all four corners and leave the sides unmarked
    • Put one tick mark on just two sides and draw one arc in a corner
    • Draw arc marks at all four corners and one tick mark on one side

  7. A diagram shows a square symbol at the corner of two lines. What is the size of that angle?

    • 45°
    • 90°
    • 180°

  8. A shape has two sides with a single tick mark and two other sides with a double tick mark. What does this mean?

    • The single-tick sides are equal to each other, and separately the double-tick sides are equal to each other
    • All four of those sides are exactly the same length
    • The double ticks mean that pair is longer than the single-tick pair

  9. What is the least number of geometric markings needed to show that a quadrilateral is a kite?

    • Two
    • Three
    • Four
    • Five

  10. In a shape, sides AB and BC both have a single tick mark. Side CD has a double tick mark. Which side is equal in length to AB?

    • BC
    • CD
    • Both BC and CD
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Reading marks in a geometry diagram W1-mt_e4V6hvcuEJ-s1

  1. The angle there is a right angle, 90 degrees · The small square is the standard symbol for a right angle. It saves you from writing 90 degrees every time.
  2. A right angle (90°) · A small square always marks a right angle, which is exactly 90°.
  3. True · The middle letter in three-letter angle notation always names the vertex.
  4. The two sides are equal in length · Matching tick marks are a shortcut for 'these lengths are equal', so you don't need to measure them.
  5. False · Four tick marks only prove the sides are equal. A rhombus has four equal sides too. You also need a right angle mark to force the shape to be a square.
  6. Put one tick mark on each of the four sides, and draw one small square in a corner · A square needs four equal sides and a right angle. Four tick marks show the sides all match, and one small square shows a right angle. That is five markings in all.
  7. 90° · The square symbol is a fixed rule for a right angle, which measures 90° every time.
  8. The single-tick sides are equal to each other, and separately the double-tick sides are equal to each other · Different tick counts mark different pairs. Same tick count means those sides match each other, not the other pair.
  9. Three · Three markings do it: one small square where the diagonals cross shows they are perpendicular, and two tick marks show one diagonal is cut into equal halves.
  10. BC · AB and BC share the same tick mark, so they match. CD has a different mark, so it belongs to a separate equal pair.
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