Are the Lines Parallel? Angles and a Transversal
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Grade 8 Math · Teaching handout
Are the Lines Parallel? Angles and a Transversal
Teaches how to decide whether two lines are parallel from the angles a transversal makes with them: equal corresponding or alternate angles, or co-interior angles that add to 180°.
Print handout
Your first print is free, with no sign-in. Then 10 sheets a month with a free account. Prints on Letter paper, or print on A4.
Print the answer key for Try it together
- Grades
- Grade 8
- Pages
- 1
- Time
- About 15 minutes
- Answer key
- Included, for Try it together
- Printing
- Tinted accents, also fine in black and white
What is on a handout
- The big idea: the rule, in a few short sentences.
- Watch me: worked examples, each with why it changes as it does.
- Watch out: the mistakes children often make, struck through beside the right answer.
- Try it together: a few items or problems to do as a class, with an answer key.
- On your own: the practice sheet that comes next.
How to teach with it
- Have students draw two lines that only look parallel and a transversal across them, then measure the alternate angles with a protractor. A degree or two apart shows that looking is not proof: the angles decide.
- Read the big idea aloud, then work through Watch me together, saying why each one changes.
- Ask the class to find the mistake in each Watch out before you show the answer.
- Do Try it together as a class, check it with the answer key, then hand out the practice sheet.
Practice worksheets
After the handout, in this order: the main practice sheet first, then more practice, then quick checks.
