6.1 – RATIOS & PROPORTIONSGeometry C1

Mr. Hughes

OBJECTIVES

1. Solve problems by writing and solving proportions.

RATIOS

If a and b are two quantities and b ≠ 0, then the “ratio of a to b” is

or it this can also be written as a : b

We can use ratios to represent the relationships between side lengths or angles of two figures

RATIOS

For example…

The ratio of a side length in ∆ABC to a length in ∆DEF below can be written as , or 2 : 1 (not 1 : 2, because the order of the ratio should correspond with the order we were told to write the ratio)

RATIOS

Ratios are usually written in their simplest form, so we want to reduce our ratio when possible.

A ratio of 7 : 14 reduces to 1 : 2.

We also never write ratios in mixed units, so we always have to convert one of the units to the other, so that our ratio is in the same unit of measurement.

COMPLETED OBJECTIVES

Solve problems by writing and solving proportions.

HOMEWORK

Textbook pages 360–363 #3–13, 18, 20–22, 42–43, 53, and 65