## Binary number 10101 is equivalent to its decimal equivalent ___?

A. 10

B. 20

C. 21

D. 111

### Answer

Correct Answer: **C. 21**

### Detail about MCQs

To convert the binary number 10101 to its decimal equivalent, you can use the positional notation system. Each digit in a binary number represents a power of 2, starting from the rightmost digit as 2^0, then increasing by one power for each subsequent digit to the left.

So, 10101 in binary is calculated as:

1 * 2^4 + 0 * 2^3 + 1 * 2^2 + 0 * 2^1 + 1 * 2^0 = 16 + 0 + 4 + 0 + 1 = 21

Therefore, the correct answer is:

C. 21