Find equivalent resistance??

Req = 50 Ω

Explanation:

The equivalent resistance is basically the sum of all the resistances in a circuit.

The sum of these resistances will depend whether these resistance are in series or parallel.

If the resistances are on series, the expression to use is:

R = R₁ + R₂ + R₃ + Rₙ   (1)

If the resistances are on parallel then the expression to use is:

1/R = 1/R₁ + 1/R₂ + 1/Rₙ    (2)

Now, according to the picture, we have R₁ and R₄ in series, so here we have to use (1):

R₁₄ = 10 + 30 = 40 Ω

R₂ and R₃ are in parallel so we use (2):

1/R₂₃ = 1/20 + 1/20 = 2/20 = 1/10

R₂₃ = 10 Ω

Finally, R₁₄ and R₂₃ are in series (Because of the sum of the resistance in each side, they are now forming one resistance in each side), therefore, we use (1) again to get the equivalent resistance of the whole circuit:

Req = 10 + 40

Hope this helps

yup its correct its: c) b b