Grade 4 - Progress in Mathematics

Expressions and Variables

2-4

A mathematical expression is a name for a number.

It does not have an equals sign.

It may involve addition or subtraction.

10 
 14 12 
 12 addition expressions

30  6 28  4 subtraction expressions

Yo u can write an expression

based on information in a problem.

Mel has 7 bananas. He eats 3 of them.

What expression shows how many bananas Mel has left?

total number of bananasnumber of bananas Mel eats

7  3

So, 7 3 shows how many bananas Mel has left.

Yo u can use a letter, or a variable, to stand

for an unknown number in an expression.

Sara has 11 apples. She uses someto bake a pie.

What expression shows how many apples Sara has left?

total number of applesunknown number of apples used

11  a

So, 11 ashows how many apples Sara has left.

Yo u can find the value of an expression with a variable.

• Substitute a number 11
  n, when n 8
  for the variable:


• Compute: 11
  8
  Value of the expression: 19

variable

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