3rd Grade - Angles

 
     
 
     
 
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3rd
Shapes and Geometry
Angles
Identify right angles in geometric figures or in appropriate objects and determine whether other angles are greater or less than a right angle.
Measurement and Geometry: right angles The ability to identify right angles (90 degree angles) and say whether other angles are greater or lesser than a right angle. The ability to tell the difference between a right angle and a bigger angle (obtuse) and smaller angle (acute). The child will be able to find and compare different types of angles in everyday life.
 

Sample Problems

(1)

What is a right angle? 90 degree angle

(2)

How are other angles different from right angles? Some are greater or lesser than 90 degrees.

(3)

Do other angles have names? Yes, angles less than 90 degrees are called acute angles and angles greater than 90 degrees are called obtuse angles.

(4)

How do these angles show up in real-life settings? Angles are seen everywhere when two line segments come together.

(5)

How are angles measured? There are standardized tools to measure angles precisely.

Learning Tips

(1)

Make sure that your child can recognize a right angle on sight. Look around your house for examples. Some that you might find are the 4 corners of a book cover, the corners on a piece of notebook or copy paper, the angle formed where a bookshelf meets the wall of the bookcase, windowpane corners, the corners on a CD case, etc.

(2)

We expect some items to contain a right angle, and perhaps they did at one time, but if your child measures now, it will not prove to be the case. One example commonly suggested to children is to look at the corner of a room, or the corner where a floor meets the wall, but houses settle and most of these are, in fact, not right-angles. Once your child is old enough to use measuring and testing tools to judge right-angles, these examples are not good suggestions.

(3)

Make sure that your child knows that we have standardized tools with which we can measure the size of an angle. “Standardized” means that all of these tools use the same scale; we don’t make up our own measuring scale. When we measure an angle we put the corner or end-point (on a protractor) right at the point, or intersection of the two lines, of the angle. When one line of the right angle is laid along the edge of the measuring tool, the angle size is read on the scale by reading where the other line crosses the tool’s scale. By definition, a right angle will always measure 90 degrees on the scale.

(4)

All angles that measure smaller than 90 degrees are called “acute angles.” One easy “trick” that can help a child remember the name is to ask your child to picture a pair of scissors. When a child cuts with scissors the angle made by the two blades will be less than 90 degrees; a child’s hand cannot stretch the scissors open wide enough to create an angle greater than 90 degrees. Let your child observe this for him/herself, and then make the “joke” that he/she is cutting with a cute pair of scissors. (a cute = acute)

(5)

An angle greater than 90 degrees is called an “obtuse” angle. Your child might enjoy shaping his body into an obtuse angle: Sit up straight on a padded floor, back straight, legs out in front. (right angle) Start bending backward at the hips, as far back as he/she can bend and not fall backward. Even a slight backwards bend at the hips forms an obtuse angle.

(6)

If a child has difficulty understanding angles, have a few friends over and let the children use their own bodies to make angles, with arms to begin with and later entire bodies on the carpet. By looking at these body formations, other children can observe and identify right angles and lesser or greater angles. Children can cut paper or real pieces of a pizza or pie and discuss the shape that remains (as well as the shapes they cut) in terms of greater, lesser or equal to a right angle.

Extra Help Problems

(1)

1-25 Complete the exercises on the attached activity pages.

 

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