Not Enough Mashed Potatoes for Thanksgiving?
Every year I notice that there are not enough mashed potatoes to go around at
Thanksgiving dinner. To solve this problem I have found an old mashed potato recipe. This year I
will make the mash potatoes and I will make sure that we have enough to go around. Please help
me alter my recipe for the various numbers of people having Thanksgiving dinner at my house.
Perfect Mashed Potatoes Recipe
Ingredients:
1.5 lbs Yukon gold potatoes
0.5 teaspoon of salt
0.25 cups heavy cream
0.125 cups butter
1/16 cup milk
Serves 4 people
Remember to wash and peel the potatoes this year!
1. First of all, I have no idea why most of the recipe is written in decimals. I want to change the decimal
values to fractions. Please put the fractional equivalent for each ingredient to the right of each ingredient
on the recipe.
Ingredients:
Fraction Form:
1
1
Pounds of Potatoes
2
1
Teaspoons Salt
2
1
Cups Heavy Cream€
4
€
1
Cups Butter
€
Cups Milk
8
1
16
€
2. I understand that we might have 8 to 12 people in total at Thanksgiving. Use the ratio table below to
alter the recipe to feed 8, 10 and 12 people Use fraction
€ values unless your teacher tells you otherwise.
4
Number of People
Pounds of Potatoes
Teaspoons Salt
Cups Heavy Cream
€
Cups Butter
€
Cups of milk
€
8
1
1
2
1
2
1
4
1
8
1
€
16
3
1
1
€
2
1
€
4
1
€
8
10
12
3
3
4
1
1
4
5
€
8
5
€
16
5
€
32
4
€
€
€
€
€
€
€
€
2b. How did you go about converting this recipe for 10 people?
1
2
1
1
2
3
4
3
8
3
16
There are probably a lot of ways to do this. I divided the recipe in half to make it for two people and then
multiplied the recipe by 5 to make it for 10 people.
2c. I have decided to go ahead and make enough mashed potatoes to serve 32 people. How much of
ingredient should I use? How can you use the information in your ratio table to help you determine this?
Number of People
4
32
1
1
Pounds of Potatoes
12
Teaspoons Salt
Cups Heavy Cream
€
Cups Butter
€
Cups of milk
€
I just multiplied the 4-person recipe by 8.
2
1
2
1
4
1
8
1
16
4
2
1
1
2
€
3. I am going to test my cooking skills by following €this recipe and
€ making the mashed potatoes a couple
days early. I don’t need to feed four people, so I am going to make mashed potatoes for two people and I
will eat them all myself. Determine how much of each ingredient I will need to make mashed potatoes for
two people.
Number of People
4
2
1
3
1
Pounds of Potatoes
Teaspoons Salt
Cups Heavy Cream
€
Cups Butter
€
Cups of milk
€
I could multiply the 4-person recipe by ½.
2
1
2
1
€
4
1
€
8
1
€
16
€
€
€
€
4
1
4
1
8
1
16
1
32
4. Explain how you can determine the total amount of each ingredient to use for any number of people
attending the party.
First you could find ¼ of everything in the 4-person recipe. Then you could multiplty that 1person serving by however many people you want to serve. In the examples below n stands for the
number of people to serve.
1 n
Pounds of Potatoes
1
2 4
1 n
Teaspoons Salt
2 4
1 n
Cups Heavy Cream
4 4
1 n
Cups Butter
8 4
1 n
€
Cups of milk
16 4
( )
( )
( )
( )
( )
5. My friend’s family is having a lot of people over for Thanksgiving dinner. They are using my recipe
for mashed potatoes and are using 7.5 pounds of potatoes. How many people will their mashed potatoes
serve? Explain how you know.
Students could use proportional reasoning, a ratio table or a proportion to solve this problem. We
have included the proportion and work below:
1.5 7.5
=
4
x
Since 7.5 is 5 times greater than 1.5 we know that he is serving 5 times as many people as the
recipe serves, so 4(5) = 20 people.
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