Angles on a straight line worksheets

Angles sitting side by side along a straight line share what is left of a half turn: together they fill 180°. These free printable worksheets draw angles meeting on a line and mark one with x.

Angles on a straight line
Angles on a straight line worksheet — Adjacent angles, 180°, free printable with answer key

The answer key prints on a separate page.

What's on this sheet

The combined line-and-point sheets ask a child to decide whether the whole is 180° or 360° before subtracting. This one keeps to the straight line, so the total is always 180° and the reading is settled — which lets a child practice the arithmetic of the missing angle without also carrying the choice of which whole applies.

Why this sheet works

When more than one angle is given, the step children skip is adding the known angles before taking them from 180. Add first, then subtract once; the instruction names the total and the figure shows the ruled straight line, so the 180° is read from the picture rather than assumed.