How_To_Be_Good_At_Math

308 ALGEBRA •^ FORMULAS

Writing a formula

A formula is like a recipe, except that

in a formula we use signs and letters

instead of words. A formula usually

has three parts: a subject, an equals

sign, and a combination of letters

and numbers containing the recipe’s

instructions. Let’s look at one of the

simplest formulas, for finding the

area of a rectangle. The formula is

Area = length × width. Using algebra,

we can write this as A = lw.

Formulas

A formula is a rule for finding out the value of something.

We write a formula using a combination of mathematical

signs and letters to represent numbers or quantities.

The subject of

the formula

The recipe

(l × w)

An equals sign shows

the formula balances

A l w

Using letters

Formulas use letters instead of words,

so we need to know what the different

letters stand for. Here are the letters we

use to solve mathematical problems

that involve measurement.

When we write a formula,

we leave out the

multiplication sign.

h = height

In a formula, we can use

letters instead of writing

out all the words.

A = area

P = perimeter

V = volume

l = length

w = width

b = base

=

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