# Monday Math Quiz | Convenience Foods

*Each Monday Kayla K’s Thrifty Ways offers three tightwad word problems to practice savings calculations.*

Question 1:

You have a crazy craving for tomato soup but have no canned soup on hand. You improvise with a simple white sauce of 1 TBSP each of butter and flour, 1 C milk, and 1 C tomato juice. You find that your homemade version is much better! Is it less expensive? The canned soup is $.79 for 1 C, plus 1 C milk. Juice is $1.59 for 46 oz, milk is $3.99 per gallon, butter is $2.99 for 16 oz, and flour is $1.69 for 5 lbs, or 73 (1/4) C servings.

Question 2:

You have been spicing up your Netflix movie nights with popcorn at home. You and your special friend enjoy the Jolly brand microwave popcorn for $2.97 for six bags of 3 servings each. You have considered purchasing an air popper for $22.50. That would enable you use kernels that cost $1.49 for 2 lbs, or 23 3 TBSP servings. How many evenings must you enjoy air-popped popcorn before the air-popper pays for itself?

Question 3:

You have a coupon for $.50 off a $2.29 can of Pillsbury flaky layers biscuits, which makes 8 biscuits. Is this deal better than your go-to baking powder biscuit recipe?

Betty Crocker Baking Powder Biscuits (Yield: 10)

2 C flour ($1.69 for 73- 1/4 C servings or 5 lbs)

3 tsp Baking Powder ($2.69 for 331- 1/8 tsp servings, or 7 oz)

1/2 C Shortening ($3.99 for 113 TBSP)

3/4 C Milk ($3.29 for one gallon 2%)

**Answers**

Question 1:

You would use milk for either preparation, so you do not need to figure that in.

46 / 8= 5.75 C in one can of juice

$1.59 / 5.75= $.277 for one C juice

There are 4 TBSP in 1/4 C, so 73 x 4= 292 TBSP in 1 5-lb bag of flour

$1.69 / 292= $.006 per TBSP flour

There are 32 TBSP butter in 1 lb, so $2.99 / 32= $.093 per TBSP butter

$.277 + $.006 + $.093= $.38

**Your homemade tomato soup costs $.38,** not counting the cost of milk.

Question 2:

3 x 6= 18 servings per box

$2.97 / 18= $.165 per microwave-popped serving

$1.49 / 23= $.065 per air-popped serving

$.165 – $.065= $.10 savings per air-popped serving

$22.50 / $.10= 225

**You must use your air popper 225 times to save money.**

*Savings comes much quicker when your air-popper is purchased secondhand. You may also try generic microwave brand popcorn or grow your own corn for air-popping.*

Question 3:

$2.29 – $.50= $1.79 for 8 Pillsbury biscuits

$1.79 / 8= **$.223 per canned biscuit**

73 / 4= 18.25 C per 5 lb bag flour

$1.69 / 18.25= $.093 per C flour

$.093 x 2 = $.185 **flour in recipe
**331 / 8= 41.375 tsp per can baking powder

$2.69 / 41.375= $.065 per tsp baking powder

$.065 x 3= $.195

**baking powder in recipe**

113 / 8= 14.125 1/2 C per can shortening

$3.99 / 14.125= $.282

**shortening in recipe**

$3.29 / 16= $.206 per cup milk

$.206 x 3/4= $.154

**milk in recipe**

$.185 + $.195 + $.282 + $.154 = $.816 per recipe

$.816 / 10=

**$.082 per homemade biscuit**

*Even with the coupon, the Pillsbury biscuits cost 37% more than the homemade version.*

*Update 2/1/11: Today a sixth grade study hall student asked for help on his math homework. He was practicing calculating percent increases. I wanted to make sure I game him similar instructions as his teacher would, so together we checked the instructions in his textbook. According to his textbook, the correct way to figure a percent increase is to subtract the original from the increase,*

*$.223 – $.082= $.141, amount saved per biscuit
*

*and then divide that number by the original.*

*$.141 / .223= .63*

*So, you save 63% by making homemade biscuits.
*

*My original calculation of simply dividing .082 by .223 showed that the homemade biscuits cost 37% of the cost of the Pillsbury biscuits.*

*I can reassure my students that they *will* use math in real life! *

For question number two:

Forget the air popper.

In a paper lunch bag, cover the bottom of the bag in one layer of kernels and spray lightly with cooking spray. Fold the top of the bag down and tape closed. Microwave until popping stops.

Generic cooking spray: $1.79

Paper lunch bags: $1.00/bag of 100

So, without actually doing the math for real, since I don’t have the products on hand at the moment. I would guesstimate that this frugal way of popping corn would add maybe two cents to the air popper price, but would eliminate the need to spend the money on the air popper or store it.

Hey, awesome! Thanks for the tip!

I am constantly amazed at all the ways that other frugalists save money. Thank you, Amy, for that wonderful tip. The power of the internet means that we don’t have to meet, but we can share ideas and learn from countless other people.

Kayla, you will make a great math teacher. Your students will appreciate your creativity in writing math questions that affect them directly. When the question deals with everyday living, students are more interested, pay more attention, and remember the lessons better. Good for you for learning this trick!

Wow, groceries are expensive where you live! Here in the Midwest, a gallon of milk is 1.99 at Aldi, flour is often available for .98 for 5#, and I can get Jolly brand popcorn for .98 – .50 coupon most of the time (just a few examples). Even a can of name brand tomato soup costs less than .25 on sale w/coupon (often closer to FREE). I count myself blessed that we eat for less; from scratch, as you’ve pointed out, is often much cheaper.

I will be checking out your blog for some tips! Judging from your blog title I only live about three hours away from you so the grocery prices should not vary that much. I did the “research” for this article at HyVee which tends to be more pricey than Aldi options.