Answer to Question 3

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Here's the circuit again:

First we will look at the parallel combination:

Add the 500 ohm and the 600 ohm resistors together to get 1100 ohms.

Now work out the single equivalent resistor for a 200 ohm and a 1100 ohm combination:

1      = 1    +   1   = 0.005 + 9.091 x 10-4 = 0.00591 ohm-1

Rtot    200      1100

 

Note how we have used the decimal reciprocals.  Do this if you forget how to add common fractions!

 

Rtot       1         = 169 ohms

            0.00591