Exercise 23 Page 16

We are given the following table.

Dish Soap Prices
Brand	Price
Lots of Suds	$0.98 for 8 ounces
Bright Wash	$1.29 for 12 ounces
Spotless Soap	$3.14 for 30 ounces
Lemon Bright	$3.45 for 32 ounces

We want to determine which brand costs the least per ounce. We can do this by finding the cost per ounce of each brand's dish soap. Let's start with Lots of Suds. We know that 8 ounces of this brand's dish soap costs $ 0.98. We can write a rate to show this situation. $ 0.98/8ouncesRecall that a unit rate is a rate that has been reduced to a denominator of 1 unit. In this case, the unit rate is the cost per ounce of dish soap. Let's find the unit rate! We can ignore the units for now to keep things simple.

0.98/8

ReduceFrac

a/b=.a / 8./.b / 8.

0.98/ 8/8/ 8

UseCalc

Use a calculator

0.1225/8/8

QuotOne

a/a=1

0.1225/1

RoundDec

Round to 2 decimal place(s)

0.12/1

We found the unit rate! $ 0.98/8ounces ≈ $ 0.12/1ounce As we can see, dish soap from Lots of Suds costs about $0.12 per ounce. We can find the unit rate for the other brands by following the same steps.

Brand	Price	Rate	Unit Rate
Lots of Suds	$0.98 for 8 ounces	$ 0.98/8ounces	$ 0.98 ÷ 8/8ounces ÷ 8 ≈ $ 0.12/1ounce
Bright Wash	$1.29 for 12 ounces	$ 1.29/12ounces	$ 1.29 ÷ 12/12ounces ÷ 12 ≈ $ 0.11/1ounce
Spotless Soap	$3.14 for 30 ounces	$ 3.14/30ounces	$ 3.14 ÷ 30/30ounces ÷ 30 ≈ $ 0.10/1ounce
Lemon Bright	$3.45 for 32 ounces	$ 3.45/32ounces	$ 3.45 ÷ 32/32ounces ÷ 32 ≈ $ 0.11/1ounce

Remember, the unit rate is the price per ounce of dish soap.

Brand	Unit Rate	Unit Price
Lots of Suds	≈ $ 0.12/1ounce	≈ $ 0.12 per ounce
Bright Wash	≈ $ 0.11/1ounce	≈ $ 0.11 per ounce
Spotless Soap	≈ $ 0.10/1ounce	≈ $ 0.10 per ounce
Lemon Bright	≈ $ 0.11/1ounce	≈ $ 0.11 per ounce

We can see that Spotless Soap costs the least per ounce. This means that C is the correct answer!