Angle pairsAngles on a line
Name: Date:
Find the angle marked x. Give each answer in degrees.
1 degrees
2 degrees
3 degrees
4 degrees
5 degrees
6 degrees
7 degrees
8 degrees
Supplementary angles worksheets
Two supplementary angles sit along a straight line, so they add to 180 degrees. These free printable worksheets draw a pair with one marked x, cut from the mixed angle-pair page.
Kid stuck on one? You don’t just get the sheet.
Supplementary angles
The answer key prints on a separate page.
What's on this sheet
Split from the mixed angle-pair sheet, this page drills only the supplementary relationship, so a child fixes the fact — a straight line is 180 degrees — before the harder job of telling it apart from complementary and vertical angles.
Why this sheet works
Each figure shows two angles opening off a ruled straight line, which is the visual cue that they fill a half turn. The arithmetic is one subtraction from 180; the reading is noticing the straight line, then writing x + 115 = 180 and solving.
How this one works
One question from this sheet, worked through a step at a time.
Angles on a straight line, one is 49°
49°+x=180°
180 − 49 =131°
49°+131°=180°
from the picture, not the numbers
lines crossing:x = the angle opposite
- The two angles sit on a STRAIGHT LINE. A straight line is a half turn, which is 180 — not 90, and the picture is the only thing that tells you which.
- So the two must add to 180: x = 180 − 49 = 131°.
- If it had been the other kind you would have taken it from 90 instead and been 90° out — which is why the picture is read first.
- One more shape to know: where two straight lines CROSS, the two angles facing each other are equal — nothing is taken away at all. Subtracting there would be wrong.