■ Rule  :   Multiply the given numbers considering them without the decimal point. In the product, the decimal point is marked off  to obtain as many places of  decimal as is the sum of  the number of  decimal places in the given numbers.

 e.g. Find the products  :

(i)  2.1789  1.1             (ii)  3.82  1.45

(iii)  .7 .2  .02            (iv)  3  .3 .003  .0003

 Soln. (i)

21789  11  =  239679.    Sum of  decimal places   =  (  4 + 1 )  =  5

 2.1789    1.1    =    2.39679                    [  =         5  ]

(ii) 382  145  =  55390.  Sum of  decimal places  =  ( 2 + 2 )  =  4

 3.82  1.45  =  5.539                                           [  =         4  ]

(iii)7  2  2  =  28.   Sum of  decimal places  =  ( 1 + 1 + 2 )  =  4

 7  .2  .02  =  .0028                                         [ =          4  ]

(iv) 3  3  3  3  =  81.   Sum of  decimal places  =  6

  3  .3  .03  .003  =  .000081                         [ =          6  ]