Algebra (Period 1)

Formulas 3-7

Formulas are special equations that have known relationships.
d = rt
we can solve for r or t
r = d/t

t = d/r

What about solving for l in the following

p = 2l + 2w

first we need to isolate the variable l so let's subtract 2w first from both sides of the equation
p = 2l + 2w
-2w -2w
p-2w = 2l

now we need to divide BOTH sides by 2
p-2w = 2l
2 -----> 2
(p-2w)/2 = l

and we solved for l

What if the variable is in the denominator
3z/x = 4/y
You could solve using cross products

3zy = 4x
and then divide both sides by 4

3zy/4 = 4x/4
which becomes

3zy/4 = x or written better as 3yz/4 = x

Solve for a in the following formula for solving for the average (mean) of three items

A = (a + b+ c)/3
you could clear it of the fraction by multiplying both sides by 3
3A = a + b+ c then subtract b and subtract c froom both sides
-b -c -b -c
3A - b- c = a


Solve for r
C = 2∏r divide both sides by 2∏

C/2∏ = 2∏r/2∏
and get
C/2∏ = r

A = ½bh Solve for h
You could use cross products
2A = bh
then divide both sides by b
and get
2A/b = h


What about A = 1/R solving for R

using cross products you get AR = 1
Then divide both sides by A and get R = 1/A

Isolate that variable!!