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## Homework Statement:

- calculate the equivalent resistance of this circuit

## Relevant Equations:

- ...

i was trying to calculate equivalent resistance of this circuit

and that was my attempt :

1) i can see two parallel 20 ohm resistors so equivalent resistance = $${20 \over 2} = 10 ohm$$

2) now we are left with 20 ohm resistor and 10 ohm resistor which are connected in series so

equivalent resistance = $$20 + 10 = 30 ohm$$

textbook's answer :

the textbook tottaly ignores the resistor in the middle so the answer simply becomes $${20 \over 2} = 10 ohm$$ which does not make any sense to me , why should i ignore the resistor in the middle ? and when should i ignore a resistor ?

thanks in advance.

and that was my attempt :

1) i can see two parallel 20 ohm resistors so equivalent resistance = $${20 \over 2} = 10 ohm$$

2) now we are left with 20 ohm resistor and 10 ohm resistor which are connected in series so

equivalent resistance = $$20 + 10 = 30 ohm$$

textbook's answer :

the textbook tottaly ignores the resistor in the middle so the answer simply becomes $${20 \over 2} = 10 ohm$$ which does not make any sense to me , why should i ignore the resistor in the middle ? and when should i ignore a resistor ?

thanks in advance.