Brain Teasers
Simple Addition 2
What is in the one's digits place in the number that is the sum of 1+2+3+...+999,998+999,999+1,000,000?
Answer
Zero.Because the sum contains the addition of the following sum in the one's digits place 100,000 times:
0+1+2+3+4+5+6+7+8+9=45
We can deduce that:
100,000 x 45 = 4,500,000
and since 0 is in the one's digits place in this number, we can deduce that 0 is also in the one's digits place in the total sum since only the digits in the one's place can affect the number in the one's digits place.
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