Multiplication of 2 numbers between 11-19

Thought this is not a very difficult calculation this little trick will definitely speed up the time.

eg.   12 x 14

1. Add to the first number  the second number’s last digit  OR

add to the second number the first number’s  last digit

(this operation is called Cross Addition)

12+4   = 16 = 2 +14

1. Muliply this number by 10

10 x 16=160

1. Find the product (multiplication outcome) of the last digits of each of the two numbers

2 x 4= 8

1.  Add the values of  (2) and (3) together and that is it

160+8=168

Examples : There is no need to write all 4 steps when making the calculations as they are simple and can take time ,they are just displayed here for illustration purposes.

13×19

1. 13+9=22=3+19
2. 10 x 22 =220
3. 3 x  9 =27
4. 220+27=247

16 x 17

1. 16+7=23=6+17
2. 10 x 23 =230
3. 6 x 7 =42
4. 230+42=272

18 x 15

1. 18+5=23=8+15
2. 10 x 23 =230
3. 8 x 5 =40
4. 230+40=280

12 x 13

1. 12+3=15=2+13
2. 10 x 15 =150
3. 2 x 3 = 6
4. 150+6=156

Practise: Now try to practise with the following multiplications. Once you get comfortable with this technique try to do them in your head without pen and paper.

11 x 16

12x 18

18 x 14

19 x 18

16 x 16

17 x 12

14 x 15