You can put this solution on YOUR website! convert 10101two to base ten
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To do these conversions "in your head",
Work from left to right:
The 1st bit is a 1
If the 2nd bit is 0, then double it = 2
The 3rd bit is 1, so double the 2, then add 1 = 5
4th is 0 --> 10
5th is 1, 10*2 + 1 --> 21
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