Banking Study Material

Quantitative Aptitude Multiplication Techniques

Multiplication Techniques
1) Split & Merge:
12 × 23 = 12(20+3) = 240 + 36=276
12 × 23 = (10+2)23 = 230 + 46 =276
63 × 20 =?
44 × 50 =?
24 × 36 =?

2) (a + b)(a - b) = (a² – b²)

17 × 23 = 23 × 17 = (20 + 3) (20 – 3) = 20^2 -3^2 =400 – 9 =391
32 × 28 =?
44 × 36 =?

3) Multiplication with '5' & '25'

A) a × 5 = a × (10/2) = (a/2) × 10

Example: 36 × 5 = 36 × (10/2) = (36/2) × 10 = 18 × 10 = 180

35 × 5 = 35 × (10/2) = (35/2) × 10 = 17.5 × 10 = 175

B) a × 25 = a × (100/4) = (a/2) × 100

Example:
1) 40 × 25 = 40 × (100/4) = (40/4) × 100 = 10 × 100 = 1000
2) 60 × 25 = 60 × (100/4) = (60/4) × 100 = 15 × 100 = 1500

3) Multiplication with 11 - 19
1732 × 11 = ?

Ans: 19052

Explanation:
Initially add 0 to multiplying number i.e 01732 × 11

First 1 Multiply with 2 ( Unit digit of 1732), i.e. 1 × 2 =2

-----2 (Unit Digit of the Answer)

Next 1 Multiply with 3 (Tens Digit of Number ) i.e. 1 × 3 = 3 and add previous digit of 3 i.e. 3 + 2 = 5

----52 ( Tens Digit of the Required Answer)

Next 1 Multiply with next digit i.e 1×7 =7 and add previous digit of 7 i.e. 7+3 = 10

add 0 to answer and keep 1 as carry part

--052 (1 carry part) (Hundreds Digit of the Required Answer)

Next 1 Multiply with next digit i.e. 1 ( Thousands Digit of a number), i.e. 1 × 1=1 and add previous digit of 1 i.e. 1+ 7 =8

already carry part is 1 add to 8, i.e. 8+1 = 9 (Thousands Digit of the Required Answer)
-9052
Finally Add 1 to the starting of a number ( Note: Here Add means not Addition)

Answer is : 19052

Exercises:

1) 5678 × 11 =?

2) 4793 × 11 =?