Question

three identical resistors are connected first in series and then in parallel find the ratio of equalent resistence​

Answer 1

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Answer in attachment

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Answer 2

Let the three  resistors be

$R_{1} \: R_{2} and \: R_{3}$

1) the resistors are connected in series,

Let R be the equivalent resistance,

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

2) the resistors are connected in parallel,

Let R be the equivalent resistance here,

$\frac{1}{R} = \frac{1}{R_{1}} + \frac{1}{R_{2}} + \frac{1}{R_{3}}$

$R = \frac{R_{1}R_{2}R_{3}}{ R_{1} + R_{2} + R_{3}}$

According to the question,

All three resistors are identical means all are equal  to R1..

Now , refer to the attachment given.

the equivalent ratio is 9.