# Resistor Series Parallel Formula

## To calculate the total resistance of the series circuit

$R_{t} = R_{1}+R_{2}+R_{3}$

Where,

$R_{t} = Total\,Resistance$

R1 = Resistance 1

R2 = Resistance 2

R3 = Resistance 3

## Total Resistance Of 2 Resistors Connected parallel

$R_{t} = \frac{R_{1}R_{2}}{R_{1}+R_{2}}$

Where,

$R_{t} = Total\,Resistance$

R1 = Resistance 1

R2 = Resistance 2

## Total Resistance Of 3 or more Resistors Connected parallel

$\frac{1}{R_{t}}=\frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}+——$

Where,

$R_{t} = Total\,Resistance$

R1 = Resistance 1

R2 = Resistance 2

R3 = Resistance 3

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#### Practise This Question

A box contains 10 red balls and 15 blue balls. One ball from the box is lost. Two balls are then drawn from the box and are found to be red ones. Find the chance that the missing ball is a blue ball.