Question

Multiply the following with suitable short method =455 by 999 , 401 by 399 , 4001 by 4001 , 1999 by 1999

Answer 1

Answer:

Step-by-step explanation:

455*999

=(455)(1000-1)

= 455000-455

= 454545

401*399

=(400+1)(400-1)

=400²-1²   (a²-b²=(a+b)(a-b))

=40000-1 = 39999

4001*4001

(4000+1)(4000+1)     [ (a+b)²=a²+b²+2ab ]

=4000²+8000+1

= 16000000+ 8000+1

= 16008001

1999*1999

= 1999²

=(2000-1)²    [ (a-b)²=a²+b²-2ab ]

=2000²+1²-2*2000*1

=4000000+1-4000

=3996001