Reply To: How do I solve this problem.

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August 4, 2021 at 9:55 am #13379
Susan Brown
Keymaster

    70 ohms is the answer.

    I think you are mixing up Total Resistance of loads in series with the Equivalent Resistance of loads in parallel.

    Series circuit: total resistance is the sum of all resistances (loads) in the circuit.

    Parallel circuits: equivalent resistance will always be less than the smallest of the resistances, and can be calculated with the formula
    Req = 1/(1/R1 + 1/R2 +…)

    Equivalent resistance is a way of taking two or more parallel loads/circuits and combining them into one theoretical resistance. It lets you know what the resistance of those parallel circuits are from the perspective of the power supply.