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What belongs in each mystery box?

Every mystery box holds the same value. Make the two sides balance.

3 × ? + 428Equal values make a level balance.

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ScienceAges 10-12Physics (O Level): Electricity & magnetism
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Series & parallel resistor networks

Two resistors of 25 Ω and 17 Ω are connected in series across a circuit. Calculate their combined equivalent resistance.

Calculate equivalent resistance for resistors in series (R₁ + R₂) or in parallel ((R₁ × R₂) ÷ (R₁ + R₂)).

+−R
Series: R₁ = 25 Ω, R₂ = 17 Ω · R_eq = R₁ + R₂ = ?
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