Expressions 4th Grade

Expressions An expression has numbers and operation signs, but no equal sign. Expressions can include parentheses and different operations (+, -, x). Sue had 12 flowers. Lily gave her 4 more flowers. Sue gave her teacher 3 of her flowers. How many does she have left? 12 flowers plus 4 flowers, minus 3 flowers (12 + 4) – 3 16 – 3 13

Expressions (Example A) Find the value of (9 – 5) + 2 (9 – 5) + 2 Subtract 5 from 9 4 + 2 Add 4 and 2 6 So, the value of (9 – 5) + 2 is 6

Expressions (Example B) Find the value of 9 – (5 + 2) 9 – (5 + 2) Add 5 and 2. 9 – 7 Subtract 7 from 9 2 So, the value of 9 – (5 + 2) is 2

More Expressions Mrs. Wallace has 30 pencils. She gave 8 to the boys and 10 to the girls. 30 – (8 + 10) 30 – 18 12

Practice Expressions 12 – (3 + 4) (8 – 5) + 9 32 + (8 + 2) 25 – (10 – 5)

Expressions with Variables You can use a variable, or letter, to stand for any number that you do not know. Then write the expression. 8 + m

Expressions with Variables Fergus planted 3 rows in his garden in the morning. In the afternoon, he planted some more rows. What expression can you write to show the total number of rows he planted? 3 + n How many rows did Fergus plant in all if he planted 4 rows in the afternoon? To find the value of the expression, replace n with the number of rows planted in the afternoon. 3 + 4  Replace n with 4 since he planted 4 rows in the afternoon 7 So, Fergus planted 7 rows in all

Expressions with Variables (Example A) Find the value of 9 – c if c = 2. 9 – c Replace c with 2 9 – 2 Subtract 2 from 9 7 So, the value of the expression is 7.

Expressions with Variables (Example B) Find the value of 8 + (m – 2) if m = 6. 8 + (m – 2) Replace m with 6 8 + (6 – 2) Subtract 2 from 6 8 + 4 12 So, the value of the expression is 12

Write an Expression Eight people were at the party, then 7 more arrived. Mike had 21 toy cars. He gave 4 of them to a friend, then got 5 more.

Write an Expression The class collected 15 bags of trash, then collected 12 more bags. A room had 25 desks. Five desks were added, then 3 were removed.

There were 24 students in the class, but some were absent. Write an expression. Choose a variable for the unknown. Tell what the variable represents. There were 24 students in the class, but some were absent. Chris had 18 cards. Then he bought some more, but lost 7.

Write an expression. Choose a variable for the unknown Write an expression. Choose a variable for the unknown. Tell what the variable represents. Susan had 24 stamps. She used some of the stamps to mail letters. There were 4 pizzas at the party, then people ate 3 of them and ordered some more. Nancy had 23 books. Her dad bought some books and gave Nancy all but 3 of them. Carly starts with 37 pieces of candy. She gives one piece to each student in her class, and one to each of her 2 brothers.

Find the value of each expression 5 + 2 + 6 (8 – 7) + 1 6 – (3 + 2) 17 – 9 – 6 (25 – 10) + 8 (62 – 40) + 31

Find the value of each expression if g =6, a = 12, and b = 7. (b + 6) + a