Convert 1101₂ to base 10.

**The reasoning** Binary (base 2) uses only 0s and 1s, where each position represents a power of 2. Reading from **right to left**: 1101₂ = (1 × 2³) + (1 × 2²) + (0 × 2¹) + (1 × 2⁰) Let me break it down: - 1 × 2³ = 1 × 8 = 8 - 1 × 2² = 1 × 4 = 4 - 0 × 2¹ = 0 × 2 = 0 - 1 × 2⁰ = 1 × 1 = 1 Add them up: 8 + 4 + 0 + 1 = **13** **Why the wrong options tempt you** **A) 11** — You might have just counted the number of 1s (three 1s) plus something random, or added the digits: 1+1+0+1 = 3... this doesn't work for base conversion! **C) 15** — This is 1111₂. Easy to confuse if you misread the question. **D) 21** — Maybe you treated it like base 10 and subtracted 8? Total confusion. **Quick takeaway** Remember **"Powers of 2 from the right"**: each position is worth 1, 2, 4, 8, 16... Multiply each binary digit by its position value, then sum everything up!