Chocolate Cookie Recipe (Fractions)

Introduction

Rex enjoys eating chocolate chip cookies. He knows he eats too many of them so his is going to try and cut down on his cookie consumption. To do this, he wants to make only about 1 1/2 dozen cookies. Rex needs help cutting his three-dozen cookie recipe in half.

Challenge

Rex is trying to cut down on his cookie consumption. He needs help to halve the recipe. In this activity you will:

cut Rex's cookie recipe in half;
determine which of two measuring cups will better measure ingredients;
calculate the number of tablespoons needed to measure the cookie ingredients.

Start Excel

Open Chocolate Chip Cookie Recipe Template.xls in Microsoft Excel.

Listed on the Excel worksheet are the ingredients for Rex's favorite chocolate chip cookie recipe. This recipe will make about three-dozen cookies.

Halving the Recipe

In cell E3, type the formula =1/2*C3
This formula multiplies the number in cell C3 by 1/2.
On the keyboard, press Enter.

To fill the formula down the column:

Click in cell E3.
Click on the black handle in the lower right corner of cell E3 and drag down to cell E12.

Dealing With Fractions
Notice the values in cells E4 and E6.

Rex has another problem, he doesn't have a 3/8 measuring cup. Again, he will need your help.

Using Another Cup

Rex has a measuring cup that is 1/3 cup and another that is 1/2 cup. By subtracting fractions you can help him decide which cup more closely measures 3/8 cup.

In cell B14, type the formula =1/2-3/8
On the keyboard, press Enter.
In cell B15, type the formula =3/8-1/3
On the keyboard, press Enter.

Which Cup is Better?

In the Insert answer here… space (cell C14), explain which cup would be better to measure 3/8 cup: 1/2 cup or 1/3 cup?

If Rex used the 1/2 cup, would he need to poor a little more sugar or a little less sugar to have 3/8 of a cup?
If Rex used the 1/3 cup, would he need to poor a little more sugar or a little less sugar to have 3/8 of a cup?

Using Tablespoons

At the bottom of the Excel worksheet, click on the Using Tablespoons worksheet tab.
Notice the values in cells E3, E4 and E6.

Rex also has a tablespoon. He learned that there are 16 tablespoons in a cup. You can determine how many tablespoons measure 1/8 cup and 3/8 cup by multiplying 16 by 1/8 and 3/8. To do this in Excel:

In cell B14, type the formula =16*1/8
On the keyboard, press Enter.
In cell B15, type the formula =16*3/8
On the keyboard, press Enter.

Using Tablespoons to Measure

In the Insert answer here… space (cell C14), explain which method Rex should use to measure 3/8 cup: using cups or using tablespoons.
Can you think of another method that Rex might use to measure 1/8 and 3/8 cup?

Extension

Rex is having a slumber party and he wants to make chocolate chip cookies for all his friends. He figures if he makes 1 1/2 recipes he will have enough cookies for all his friends to enjoy.

At the bottom of the Excel worksheet, click on the More Recipe worksheet tab.
In cell E3, type the formula =1 1/2*C3
Tip:- Make sure you type a space between 1 and 1/2.
On the keyboard, press Enter.
Fill the formula down the column.

Answer the Following

In the Insert answer here… space (cell C14), explain how Rex could measure each of the ingredients.
The chocolate chips come in two weights: 6 and 12 ounces. Explain how Rex could measure 9 ounces of chocolate chips.