Algebraic Expressions
This lesson covers solving different algebraic expressions. Algebraic expressions are number sentences that include a letter that must be solved for a value. 24 + n = 45 is an example of an algebraic expression typical in fourth grade. I wrote a song that describes the process we use for solving for the letter (variable). It is to the tune of "Happy Birthday" and goes:
If the blank is in the middle
For subtraction and division
Do the same as the symbol
To get the answer right
(Then students should know that for every other situation, they do the opposite of the symbol. Addition's opposite is subtraction. Multiplication's opposite is division. Students also need to know that there are three ways to "express" multiplication: x, the dot, and no symbol at all.)
Students will also need to look at the "Basic Vocabulary" video and use this information to create algebraic expressions. The video lesson can be viewed by clicking on the play button. You can also access practice problems for creating and solving algebraic expressions, word problems, and an answer key below.
If the blank is in the middle
For subtraction and division
Do the same as the symbol
To get the answer right
(Then students should know that for every other situation, they do the opposite of the symbol. Addition's opposite is subtraction. Multiplication's opposite is division. Students also need to know that there are three ways to "express" multiplication: x, the dot, and no symbol at all.)
Students will also need to look at the "Basic Vocabulary" video and use this information to create algebraic expressions. The video lesson can be viewed by clicking on the play button. You can also access practice problems for creating and solving algebraic expressions, word problems, and an answer key below.
Demonstration by: Anna Claire and Jose
Practice Problems


Sample Word Problems:
Try to solve and figure out which equation you could have used.
1. Tommy has three times as many cupcakes as Molly. Molly has 33 cupcakes. How many cupcakes does Tommy have?
Which equation could you use to solve for this answer? 3 + n = 33 3n=33 33  n = 3 33 x 3 =t
2. Nathan has 24 books on his bookshelves. Maggie took some of the books. Now Nathan only has 15. How many books did Maggie take? Which equation could you use to solve for this answer? 24  n = 15 24 + n = 15 24 n = 15 15 n = 24
3. If each package of pencils contains ten pencils, how many packages would it take to package 200 pencils?
Which equation could you use to solve for this answer? 10  n = 200 10 + n = 200 10 n = 200 200 x 10 = n
4. Carmen counted twentyone pennies into three sacks. How many pennies did she put into each sack?
Which equation could you use to solve for this answer? 21 x 3 = n 21  3 = n 21 n = 3 3 n = 21
5. Hunter added some playing cards to the top of the card pile. Rosalie counted 63 cards. A regular playing deck has 52 cards. How many cards did Hunter add to the deck?
Which equation could you use to solve for this answer? 63  n = 52 52 + n = 63 52  n = 63 63 + n = 52
Try to solve and figure out which equation you could have used.
1. Tommy has three times as many cupcakes as Molly. Molly has 33 cupcakes. How many cupcakes does Tommy have?
Which equation could you use to solve for this answer? 3 + n = 33 3n=33 33  n = 3 33 x 3 =t
2. Nathan has 24 books on his bookshelves. Maggie took some of the books. Now Nathan only has 15. How many books did Maggie take? Which equation could you use to solve for this answer? 24  n = 15 24 + n = 15 24 n = 15 15 n = 24
3. If each package of pencils contains ten pencils, how many packages would it take to package 200 pencils?
Which equation could you use to solve for this answer? 10  n = 200 10 + n = 200 10 n = 200 200 x 10 = n
4. Carmen counted twentyone pennies into three sacks. How many pennies did she put into each sack?
Which equation could you use to solve for this answer? 21 x 3 = n 21  3 = n 21 n = 3 3 n = 21
5. Hunter added some playing cards to the top of the card pile. Rosalie counted 63 cards. A regular playing deck has 52 cards. How many cards did Hunter add to the deck?
Which equation could you use to solve for this answer? 63  n = 52 52 + n = 63 52  n = 63 63 + n = 52
Check Your Work!
answerkeyalgebraicexpressions.doc 