Aptitude

Question

what is the unit digit in

$(3474)^{1793}*(225)^{317}*(451)^{491}$

Comments

0?

---

yes,answer should be zero.

Answer 1

4   ;  4*4=16  ;  4*4*4=64  ;   4*4*4*4=256   ;  4*4*4*4*4=1024 

you can see Here  if  number of 4 in unit place is odd then unit digit will be 4 and number of 4 in unit place is even then unit digit will be 6.

Now

5  ;   5*5 =25   ; 5*5*5=125 ; 5*5*5*5=625

Here unit digit will be 5 always.

1 ;   1*1 =1  ;  1*1*1 =1 ;  1*1*1*1=1

Here unit digit will be 1 always.

 (3474)¹⁷⁹³  :-  Here number of 4 in unit place is odd so unit digit will be 4.

(225)³¹⁷ :- Here unit digit will be 5.

(451)⁴⁹¹ :- Here unit place result will be 1. 

 So unit digit in ( 3474)1793 *( 225 )317 * ( 451 )491}

4*5*1=20

Hence unit digit in  ( 3474)1793 *( 225 )317 * ( 451 )491  will be ZERO.

Answer 2

Any number of power in $5$ gives unit digit as $5$. when $5$ multiply with any even number its unit digit is $0$.

$4^{odd}=4,$so $4*5=20=0$

therefore UD=$0$