For example
The edge of a ruler is straight, but a rope is not.
In Grade 1
Children test edges against a ruler or a folded paper to decide whether a line is straight.
Watch out for
Children often call a gently bending line straight. Hold a ruler against it: a straight line touches all the way along.
Say it at home
Hunt for straight edges around the room and check each one against a ruler.
Try it together
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