Thursday , December 9 2021
Mathematics

NCERT 5th Class (CBSE) Mathematics: Introduction To Algebra

We know that a mathematical expression uses mathematical symbols instead of words. For example, the words ‘twenty-eight increased by five’, will be shown as the mathematical expression 28 + 5.

Can you give the mathematical expressions for these words?

  1. Seventy three minus forty -two
  2. Twelve less two
  3. Six times fifteen
  4. Thirty plus eleven take away nine

Sometimes, in a mathematical expression, we use letters to represent numbers we do not know.

If we say that there were some people at a party and 7 people left, we can show this as an expression, n-7, where n represents the number of people in the party.

If there were 12 people at the party, then n would represent 12. If there were 20 people at the party, then n would represent 20.

These letters are called variable because they can represent any number.

CHECKPOINT: When we write an expression using variables, words and/or operations, it is called an algebraic expression.

Let p be the number of pencils in your pencil box. Study the algebraic expressions for each:

12 pencils more than the number of pencils in your box → p + 12 or 12 + p

4 pencils less than the number of pencils in your box → p – 4

Three times the number of pencils in your box.  → 3 × p also written as 3p

The number of pencils in your box divided by 4  → p ÷ 4 also written as p/4

Here, the expressions have been put into words. The unknown number or the variable is w.

18 + → w added to 18

10 – w subtracted from 10

7→ The product of w and 7

6 ÷ → 6 divided by w

If we know that w = 3, Then expressions above can be simplified and a value can be obtained for each expression.

If we substitute 3 in place of w, we get

18 + w = 18 + 3 = 21

10 – w = 10 – 3 = 7

7w = 7 × 3 = 21

6 ÷ w = 6 ÷ 3 = 2

Check Also

5th class NCERT Hindi Book Rimjhim

बिशन की दिलेरी 5th NCERT CBSE Hindi Book Rimjhim Ch 15

बिशन की दिलेरी 5th Class NCERT CBSE Hindi Book Rimjhim Chapter 15 प्रश्न: इन वाक्यों को अपने …