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Find the units digit of 1^5 + 2^5 + 3^5 + ... + 123^5.

 Dec 28, 2019
 #1
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+1

sumfor(n, 1, 123, n^5) = 591,309,561,876

 Dec 29, 2019
 #2
avatar+2850 
+1

Find units digit of each term

 

1^5 is 1

 

2^5 is 2

 

3^5 is 3

 

See the pattern here?

 

Its 1 + 2 + 3... 121 + 122 + 123

 

So (123)*(124)/2 = 7626.

 

The units digit of that number is \(\boxed{\sqrt{6}}\)

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 Dec 29, 2019
 #3
avatar+108734 
+1

 

Find the units digit of 1^5 + 2^5 + 3^5 + ... + 123^5.

 

looking at the last digit for each one

1+2+3+4+5+6+7+8+9+0 = 45

45*12 = 540

540+1+2+3=546

 

So I think the last digit is 6

 

Where did that squareroot come from CalculatorUser?

 Dec 29, 2019

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