Simple Expressions

Class 7 Maths · Chapter 2: Arithmetic Expressions · NCERT Ganita Prakash section 2.1

Learn

Phrases like 13 + 2, 20 − 4, 12 × 5 and 18 ÷ 3 are arithmetic expressions. Every expression has a value, the number it works out to: the value of 13 + 2 is 15, and we write 13 + 2 = 15. Zoya spends ₹30 on her school bus every day, Monday to Friday: her weekly cost is the expression 5 × 30, read "5 times 30".

5 × 30 = 150

Many expressions, one value: 12 can be 10 + 2, 15 − 3, 3 × 4 or 24 ÷ 2. And we can compare expressions by their values: 10 + 2 > 7 + 1 because 12 > 8; 13 − 2 < 4 × 3 because 11 < 12.

10 + 2 > 7 + 1

Compare without calculating: which is more, 1023 + 125 or 1022 + 128? Imagine Kabir has 1023 stickers and gets 125 more; Meher has 1022 and gets 128 more. Kabir started with 1 more, but Meher got 3 more, so Meher ends with 2 more: 1023 + 125 < 1022 + 128.

1023 + 125 < 1022 + 128

For subtraction, think of losing: 113 − 25 and 112 − 24. The first starts with 1 more but also loses 1 more, so both are equal: 113 − 25 = 112 − 24. Starting bigger makes the result bigger; taking away more makes it smaller.

113 − 25 = 112 − 24

Explore: order by value.

1. Put the expressions in increasing order of value.

Remember

• An expression like 5 × 30 has a value; = links an expression to its value.
• Compare expressions by their values, often just by comparing the changes.

Quick check

Compare without calculating: 245 + 289 ___ 246 + 285

1. >
2. <
3. =

Think about it

Write three different expressions, each using two numbers, whose value is 24.

Practice

Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.