Question

How do you convert -220 degrees to radians without a calculator?

Answer 1

You probably know that `180°` corresponds to `pi` radians;
You can build the proportion:
`180°:pi=()°:(rad)`
Set `()°=-220°` and solve for `(rad)`;
you'll get:
`(rad)=-220°pi/(180°)=-22°pi/(18°)=-11/9pi`