To get the total resistance in a parallel circuit, you need to remember that unlike in a series, you do not just merely add the resistances. You need to get the reciprocal first of each resistance and add them together.
[tex] \frac{1}{R_{T}} = \frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}... +\frac{1}{R_{n}} [/tex]
After adding them, you will get the reciprocal again and then compute for the value. The problem says that there are 4 resistors in the circuit that have a resistance of 75.
[tex] \frac{1}{R_{T}} = \frac{1}{75}+\frac{1}{75}+\frac{1}{75}+\frac{1}{75} [/tex]
Add up the numerator and copy the denominator:
[tex] \frac{1}{R_{T}} = \frac{4}{75}[/tex]
Then get the reciprocal to get the total resistance:
[tex]R _{T} = \frac{75}{4} = 18.75[/tex]
The answer to your question then is A. 18.8.
