AI-generated practice question — model-generated for extra practice, not a previous-year CBSE board question.
For resistors in series: $R_s = R_1 + R_2 + R_3 = 4 + 6 + 10 = \mathbf{20\ \Omega}$
Source: Chapter 11, Section 11.6.1
For a series combination, equivalent resistance is simply the sum of all individual resistances. Examiners expect the formula, substitution, and final answer with the correct unit (Ω) — all in one line for 1 mark.