9. What digit appears in the units place in the number obtained when 2^320 is multiplied out?
A. 0
B. 2
C. 4
D. 6
E. 8

Question

9. What digit appears in the units place in the number obtained when 2^320 is multiplied out?
A. 0 
B. 2 
C. 4 
D. 6 
E. 8

anonymous · Answer

If we wanted the last digit of 2 999  , note that 996  is a multiple of 4 . So at 996  we get a 6 . Now count forward: 2 , 4 , 8 : the answer is 8 . Or else 1000  is a multiple of 4 . Go backwards one step from 6 : the last digit is 8 .

anonymous · Answer

That's a quote from : http://math.stackexchange.com/questions/177312/what-digit-appears-in-unit-place-when-2320-is-multiplied-out

anonymous · Answer

Do you understand?

anonymous · Answer

well im still loading the concept ....

unklerhaukus · Answer

$$2^1=2$$$$2^2=4$$$$2^3=8$$$$2^4={16}$$$$2^5=32$$$$2^6=64$$$$2^7=128$$$$2^8=256$$$$\dots$$
we notice last digit cycles,
2,4,8,6,2,4,8,6,2,4,6...
the pattern repeats every 4 terms

anonymous · Answer

oh ok i c that ...

anonymous · Answer

right that's helpful

unklerhaukus · Answer

so the last digit will be the same for 
$$2^{320},2^{316},...$$

anonymous · Answer

uh huh ...

unklerhaukus · Answer

$320$  is 4 times 79 +  4 

$2^{320}$ has the same last digit as $2^4$

anonymous · Answer

right ....thanx alot