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

Estimating Angles

Mathematics · Geometry · ages 9-10
Name ______________________   Date ____________

  1. Omar says a 130 degree angle is obtuse because it is bigger than 90 but smaller than 180. Is Omar right?

    Circle one:   True   False

  2. An angle measures about 130 degrees. What type of angle is it?

    • Acute
    • Right
    • Obtuse
    • Reflex

  3. An angle measures about 130 degrees. What type of angle is it?

    • Acute
    • Obtuse
    • Reflex

  4. At 3 o'clock, the clock hands form a right angle of exactly 90 degrees.

    121234567891011

    Circle one:   True   False

  5. Which of these is a reflex angle?

    • 45 degrees
    • 90 degrees
    • 135 degrees
    • 270 degrees

  6. The small angle between two lines measures 90 degrees. The reflex angle on the other side is 360 degrees minus that. What is the reflex angle, in degrees?

    Answer: ______________

  7. A reflex angle is about 270 degrees. How many degrees short of a full turn is that?

    Answer: ______________

  8. Eva orders 30, 85, 110, and 150 degrees from smallest to largest. Is Eva right?

    Circle one:   True   False

  9. Four angles: a narrow wedge, a wide open door, a straight line, and one that goes way past halfway around. Put them in order from smallest to largest.

    • narrow wedge, wide door, straight line, way past halfway
    • way past halfway, straight line, wide door, narrow wedge
    • wide door, narrow wedge, way past halfway, straight line

  10. Angles of 45, 120, 95, and 60 degrees are ordered smallest to largest. What position is 95 degrees in? Give 1 for first, 2 for second, and so on.

    Answer: ______________

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Answer key

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

Estimating Angles W1-mt_YUJ5pwalqL-s1

  1. True · Omar is right: that is exactly what obtuse means.
  2. Obtuse · 130 degrees is between 90 and 180, so it is obtuse.
  3. Obtuse · 130 degrees is more than 90 but less than 180, so it's obtuse.
  4. True · Yes. The hands make a square corner, which is a right angle.
  5. 270 degrees · 270 degrees is past 180, so it is reflex.
  6. 270 · 360 minus 90 equals 270. That's the reflex angle, going all the way around the other side.
  7. 90 · 360 - 270 = 90 degrees short.
  8. True · Eva is right: 30 < 85 < 110 < 150.
  9. narrow wedge, wide door, straight line, way past halfway · Narrow wedge is acute, wide door is obtuse, straight line is 180 degrees, and way past halfway is reflex: the largest.
  10. 3 · Ordered: 45, 60, 95, 120. 95 degrees sits 3rd.
Worksheet · LightMySky