NCERT Book Class 7 Mathematics (Part I) Chapter 2 Arithmetic Expressions

ARITHMETIC
2 EXPRESSIONS

2.1 Simple Expressions
You may have seen mathematical phrases like 13 + 2, 20 – 4, 12 × 5, and
18 ÷ 3. Such phrases are called arithmetic expressions.
Every arithmetic expression has a value which is the number it
evaluates to. For example, the value of the expression 13 + 2 is 15. This
expression can be read as ‘13 plus 2’ or ‘the sum of 13 and 2’.
We use the equality sign ‘=’ to denote the relationship between an
arithmetic expression and its value. For example:
13 + 2 = 15.

Example 1: Mallika spends ₹25 every day for lunch at school. Write
the expression for the total amount she spends on lunch in a week
from Monday to Friday.
The expression for the total amount is 5 × 25.
5 × 25 is “5 times 25” or “the product of 5 and 25”.
Different expressions can have the same value. Here are multiple
ways to express the number 12, using two numbers and any of the four
operations +, – , × and ÷:
10 + 2, 15 – 3, 3 × 4, 24 ÷ 2.

Choose your favourite number and write as many expressions as you
can having that value.

Comparing Expressions
As we compare numbers using ‘=’, ‘<’ and ‘>’ signs, we can also compare
expressions. We compare expressions based on their values and write
the ‘equal to’, ‘greater than’ or ‘less than’ sign accordingly. For example,
10 + 2 > 7 + 1

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