Multiplication Shortcut Part- 1
Change Order
Numbers may be multiplied in any orders. You can take advantage of this fact by multiplying whatever order is easiest for you.
Example:
25 × 937 × 4= 25 × 4 × 937= 100 × 937= 93700
Splitting Number
You can simplify multiplication by splitting a number into smaller parts by units (ones), tens, hundreds etc.
Example:
87 × 9= (80 + 7) × 9 = (80 × 9) + (7 × 9) = 720 + 63 = 783;
213 × 8 = (200 + 13) × 8 = (200 × 8) + (13 × 8) = 1600 + (10 + 3) × 8 = 1600 + 80 + 24 = 1704
Doubling and Halving
We can simplify some multiplication problems by doubling one factor and halving the other factor.
Example:
35 × 28 = 70 × 14 = 140 × 7 = (100 + 40) × 7= 700 + 280 = 980;
45 × 48= 90 × 24= 180 × 12= 360 × 6 = (300 + 60 ) × 6= 1800 + 360= 2160;
750 × 24 = 1500 × 12 =3000 × 6= 18000.
In the above examples we simplify these multiplication by doubling first number and halving the other number.
10- Level Number
You can made numbers near 10-level such as 9, 11, 19, 21, 29, 31… etc into easy multipliers by changing them into numbers ending in zero.
Example:
45 × 19= 45 × (20 – 1)= 45 × 20 – 45= 900 – 45= 855;
31 × 29 = (30 + 1) × (30 – 1) = 900 – 1= 899; [(a + b)(a – b)= a^2 – b^2];
99 × 97 = (100 – 1) ) × 97 = 9700 – 97 = 9700 – 100 + 3 = 9603
One Number Has All Digits Alike
If the digits of a number in multiplication are all the same, you can simplify the multiplication by making the number as multiplier.
Example:
No Carry Multiplication
Multiplication can be done without carrying wither from left to right or right to left. The zeros in the partial products help to make the addition easier.
Example:
