Page 70 - Maths Class 03

Count the stars in the above drawing.

What number is named by 5 x 3 ? (Ans. 15)
And by 3 x 5 ? (Ans. 15).

Is 5 x 3 = 3 x 5 ? (Ans. Yes)

Different ways of arranging and thinking about 12 dots are shown below.

3 groups of 4 2 groups of 6
3 x 4 = 12 2 x 6 = 12

4 groups of 3 6 groups of 2

4 x 3 = 12 6 x 2 = 12

Hence, 3 x 4 = 4 x 3 2 x 6 = 6 x 2

The above property is called commutative property of multiplication . We
can say that multiplication is commutative.

Multiplication of 3-Digit Numbers by 1-Digit Numbers

Without Regrouping

Example : Multiply 312 by 3.
H T O

H T O 3 1 2

3 1 2 x 3

x 3
3 x 2 ones = 6 ones 6
9 3 6

3 x 1 ten = 3 tens 3 0

3 x 3 hundreds = 9 hundreds 9 0 0

The sum is 9 3 6

You need not use a grid and write each partial product. Simply, multiply the

ones, tens, hundreds and thousands and write the product in appropriate

columns.

Mathematics-3 70