Question 1160816
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Think about what happens when you add 1 or subtract 1 from 100 in the familiar base 10.<br>
Adding just adds 1 to the units digit.<br>
Subtracting 1 gives 99, because 9 is the largest digit in base 10.<br>
So....<br>
A. 100 base 8
The largest digit in base 8 is 7, so
..., 77, 100, 101,...<br>
B. 10000 base 7
The largest digit in base 7 is 6, so
..., 6666, 10000, 10001, ...<br>
Then think about what happens when you add 1 to 509 in base 10.  9 is the largest digit in base 9, so adding 1 makes the units digit 0, and you "carry" a 1 to the next digit to the left: 509 + 1 = 510.<br>
C. 305 base 6
5 is the largest digit in base 6, so
..., 304, 305, 310, ...<br>