SETTING UP AND SOLVING
PROPORTIONS!
SET UP THE PROPORTION AND SOLVE!

If 12 bananas weigh 3lbs, how many bananas
would weigh 15 lbs?
FIRST SET IT UP
THEN USE CROSS PRODUCTS TO SOLVE


Multiply 15 times 12 and
then divide by 3.
If there is a shortcut go
ahead and use it!
CROSS PRODUCTS
SHORT CUT
 12
 Since
x 15= 180
 180÷3 = 60
 60 bananas
3 goes into
15 five times, just
multiply both the
top and bottom
number by 5.
 12 x 5 = 60
 60 bananas
SOLVING WITH ALGEBRA
ANOTHER WAY
 12
 12




x 15 = 3x
180 = 3x
180 = 3x
3
3
60 = x
x 15 = 3x
 180 = 3x
 180 ÷ 3 = 3x ÷ 3

60 = x
SET UP THE PROPORTION AND SOLVE!

If 12 bananas weigh 3lbs, how much would
156 bananas weigh?
MULTIPLE WAYS TO SET UP PROPORTION
IF 12 BANANAS WEIGH 3LBS, HOW MUCH
WOULD 156 BANANAS WEIGH?
MULTIPLE WAYS TO SET UP PROPORTION
YOU MULTIPLY THE SAME NUMBERS ANY WAY
YOU SET IT UP!
SOLVING WITH ALGEBRA







156 x 3 = 12x
468 = 12x
468 = 12x
12
12
39 = x
156 bananas would weigh
39 lbs.




156 x 3 =
468
=
468 ÷ 12=
39
=
12x
12x
12x ÷ 12
x
NEW TYPE OF PROBLEM.

If I can get 2 lbs of chocolate
stars for $6, how much
would it cost for 3 lbs?

It is pretty easy to solve using
cross products, but there is
also a relationship between
the numerator and
denominator. Use this
shortcut when you can!


2 x 3 equals 6, so 3 x 3= 9
The answer is $9
DIFFERENT TYPE OF PROBLEM.
 If
I can get 4 lbs of
chocolate stars for
$6, how much
would it cost for 3
lbs?
 The
answers are
not always going to
be whole
numbers!
 18 ÷ 4 = $4.50
 If
a group can
wash 10 cars in
12 minutes at a
fundraiser, how
many cars can be
washed in 18
minutes?
CAN YOU FIGURE IT OUT AN EASIER WAY?

If a group can wash 10
cars in 12 minutes at a
fundraiser, how many
cars can be washed in
18 minutes?

If you simplify the ratio,
then there is an easy
shortcut!
USING SIMPLIFYING SHORTCUT



6 x 3 = 18 so
5 x 3 = 15
15 cars can be washed
in 18 minutes
A LITTLE TOUGHER NOW!

If I can grade 25 warmups in 2 hours, how
many warmups can I grade in 5 hours?

(Round to the nearest warmup)
THE ANSWER IS??????

62.5 which rounds to 63!
YOU CAN DO IT!!!!!

My Roundup weed killer says to mix 4 fl oz of
concentrate for each 128 fl oz of water. If I
have a spray bottle that holds 40 fluid oz of
water, how much Roundup concentrate should
I add?
AND THE ANSWER IS ?????
4 x 40 = 128 x

160 = 128x
 160 ÷ 128 = 128x ÷ 128

1.25 = x
 The answer is 1.25 or 1¼ fl. oz. concentrate

WHAT QUESTIONS DO YOU STILL HAVE?