Question number 11 how did we found the answer ?

Option A. 57.14 Ω

Explanation:

From the question given above, the following data were obtained:

Resistor 1 (R₁) = 100 Ω

Resistor 2 (R₂) = 400 Ω

Resistor 3 (R₃) = 200 Ω

Equivalent Resistor (Rₚ) =?

The equivalent resistor in the above circuit can be obtained as follow:

1/Rₚ = 1/R₁ + 1/R₂ + 1/R₃

1/Rₚ = 1/100 + 1/400 + 1/200

Find the least common multiple (lcm) of 100, 400 and 200. The result is 400. Divide 400 by 100, 200 and 400 respectively and multiply the result with the numerator as shown

1/Rₚ = (4 + 1 + 2)/400

1/Rₚ = 7/400

Invert

Rₚ = 400/7

Rₚ = 57.14 Ω