`5358 xx (50 + 1)`
`=(5358 xx 50) + (5358 xx 1)`
  =267900 + 5358=273258.

`=(1307)^2`=`(1300 + 7)^2`
`=(1300)^2 + (7)^2 + 2 xx 1300 xx 7`
=1690000 + 49 + 18200
=1708249.

=unit digit in the product `(4 xx 8 xx 7 xx 3)`=2

In order to obtain 2 at the unit place it must be multiplied by a number whose unit digit is 7.
So,*must be replace by 7.

:.Unit digit in `7^68`is 1.

 :.Unit digit in `7^71`is 3. `[1 xx 7 xx 7 xx 7` gives unit digit 3]

 Again,every power of 6 will give unit digit 6.

 :. Unit digit in `6^59` is 6.

 Clearly,unit digit in `3^4` is 1.

 So,unit digit in `3^64` is 1

 :.Unit digit in `3^65` is 3.

 :. Unit digit in `(7^71 xx 6^59 xx 3^65)` is 4. `[3 xx 6 xx 3`gives unit digit 4]`