PPT: Expressions using Letter-Numbers | PPTs for Class 7 PDF Download

 Page 1


Expressions Using Letter-
Numbers
Page 2


Expressions Using Letter-
Numbers
Why Use Letters in Math?
"Why do we need to use letters in math? Numbers 
make sense, but letters?" Ravi asked Meena as they 
walked home from school.
Meena explained that letters act as placeholders for 
numbers that can change or that we don't know yet.
When we write Shabnam's age as s = a + 3, we create 
what mathematicians call an algebraic expression.
Page 3


Expressions Using Letter-
Numbers
Why Use Letters in Math?
"Why do we need to use letters in math? Numbers 
make sense, but letters?" Ravi asked Meena as they 
walked home from school.
Meena explained that letters act as placeholders for 
numbers that can change or that we don't know yet.
When we write Shabnam's age as s = a + 3, we create 
what mathematicians call an algebraic expression.
Letters as Number 
Representatives
Representing 
Relationships
Letters help us write 
expressions that 
describe patterns and 
real-world situations, 
regardless of specific 
values.
Age Example
If Aftab is 12, then a = 12, 
and Shabnam's age is: a 
+ 3 = 12 + 3 = 15 years.
Matchstick Patterns
For L-shaped patterns, the number of matchsticks is 
always 2 times the number of Ls.
Page 4


Expressions Using Letter-
Numbers
Why Use Letters in Math?
"Why do we need to use letters in math? Numbers 
make sense, but letters?" Ravi asked Meena as they 
walked home from school.
Meena explained that letters act as placeholders for 
numbers that can change or that we don't know yet.
When we write Shabnam's age as s = a + 3, we create 
what mathematicians call an algebraic expression.
Letters as Number 
Representatives
Representing 
Relationships
Letters help us write 
expressions that 
describe patterns and 
real-world situations, 
regardless of specific 
values.
Age Example
If Aftab is 12, then a = 12, 
and Shabnam's age is: a 
+ 3 = 12 + 3 = 15 years.
Matchstick Patterns
For L-shaped patterns, the number of matchsticks is 
always 2 times the number of Ls.
What's the Pattern?
35
Coconut Price
Cost per coconut in rupees
60
Jaggery Price
Cost per kilogram in rupees
4
Square Sides
Number of equal sides in a 
square
Using variables, we can create expressions like "Total cost = c × 
35 + j × 60" where c is the number of coconuts and j is kilograms 
of jaggery.
Page 5


Expressions Using Letter-
Numbers
Why Use Letters in Math?
"Why do we need to use letters in math? Numbers 
make sense, but letters?" Ravi asked Meena as they 
walked home from school.
Meena explained that letters act as placeholders for 
numbers that can change or that we don't know yet.
When we write Shabnam's age as s = a + 3, we create 
what mathematicians call an algebraic expression.
Letters as Number 
Representatives
Representing 
Relationships
Letters help us write 
expressions that 
describe patterns and 
real-world situations, 
regardless of specific 
values.
Age Example
If Aftab is 12, then a = 12, 
and Shabnam's age is: a 
+ 3 = 12 + 3 = 15 years.
Matchstick Patterns
For L-shaped patterns, the number of matchsticks is 
always 2 times the number of Ls.
What's the Pattern?
35
Coconut Price
Cost per coconut in rupees
60
Jaggery Price
Cost per kilogram in rupees
4
Square Sides
Number of equal sides in a 
square
Using variables, we can create expressions like "Total cost = c × 
35 + j × 60" where c is the number of coconuts and j is kilograms 
of jaggery.
Revisiting Arithmetic Expressions
Basic Operations
Addition, subtraction, multiplication, and division form arithmetic expressions.
BODMAS Rule
Brackets, Orders, Division, Multiplication, Addition, Subtraction.
Substitution
Replace variables with values to evaluate algebraic expressions.