Proving lines parallel: the converses
- The page cannot settle it — 3 tasks
- Which side of the argument is parallel on? — 3 tasks
- Congruent corresponding angles force parallel — 3 tasks
- Which pair proves it, and which proves nothing — 3 tasks
- What the proof rests on, and what it pays for — 7 tasks
- Practice — 24 tasks
- Summary — 2 tasks
- Cool-down — 3 tasks
Classroom activities
Things a class does rather than writes on. Each one is a finished PDF: print it, cut it up if it says so, and hand it round.
-
Proving Lines Parallel — Cut & Glue Sort 25 minutes · 5 sheets
12 marked figures to cut out and glue into 3 bins — these marks force the lines parallel, these refute it, these settle nothing — which is the whole difference between a converse and a guess, on one sheet.
-
Proving Lines Parallel — Answer Maze 10–15 minutes · 4 sheets
One page and nothing to prepare: each box marks a pair of angles and asks what the marks force, so a student who thinks two angles at one crossing prove anything is sent to a box that says why — and the row of box numbers at the foot marks the sheet in a glance.
-
Proving Lines Parallel — Mystery Picture 25–35 minutes · 4 sheets
25 figures and nothing on the sheet marked parallel: fill the square with slanted lines where the marks force the lines parallel, leave it white where they do not, and the picture that appears is the marking.
-
Proving Lines Parallel — Scavenger Hunt a full class period · 13 sheets
16 cards round the room, each giving two marked angles in terms of x and asking for the value of x that makes the lines parallel; the card whose top carries that answer is the next stop, and a wrong reading lands on a card that names the mistake and sends them back — so a clean run is 8 lines on the record sheet.