Multiplying a number by 11

To multiply any number by 11 we just put
the total of the two figures between the 2 figures.
32X11
Here  first we write 2 of 32 extreme right  ,now add up 3+2 =5 ,put 5 before 2 and write 3 extreme left .Required answer is 352
322x11
Write extreme right 2of 322  and add up  2&2 of 322  , 2+2=4  ,write 4 before  2   Now our partial answer is ...........42  .Again add up 3&2 of 322  .3+2 =5 write before ..42 .Now our partial  answer  becomes ..542  .Put 3 before 5 . Now our required answer is 3542  


 

• 77 x 11 = 847

  This involves a carry figure because 7 + 7 = 14
  we get 77 x 11 = 7₁47 = 847

  Multiplication of  22 ,33 ,44 ,55, 66 , 77 ,88 

I think all of you understand this concept . It is a very useful tool ,with the help of this tool 
now we learn multiplication of  22 ,33 .44 ,55. 66 . 77 ,88 
22x45 =( 2x11)x45 = 11x(2x45)=11x90= 990
33x66 = (3x11)x66 = 11x(3x66)=  11x198=  2178
44x356=(4x11)x356= 11x(4x356)=11x 14 24=1 5664
55x58   =(5x11)x28 = 11x( 5x28) = 11x 140  = 1540
66x23   =(6x11)x23 = 11x(6x23)  = 11x138   = 1518   
Same way 77 =7x11  and 88=8x11

Multiplication of 11 is great time saver   How ??? 
You can do calculations in  Mensuration very fast  by this tool
As you know value of  p is  22/7 .You can break it as 2x11/7  
Ex  Find the area  of  circle of radius of 14 cm

(22/7)x14x14=11x2x2x14=11x56=616square cm
  All calculation mentally,  no rough work , a great  time saver.