in an electric circuit, two resistors with resistances 3 ohm and 5 ohm are connected in parallel. in this case, if r is the combined resistance of these two resistors, then the reciprocal of r is equal to the sum of the reciprocals of two resistors. what is the value?  Pick one
A) 15 ohms	B) 15 / 8 ohms	C) 1 / 8 ohms	D) 8 / 15 ohms	E) 8 ohms
<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<gadget id="calculator">3 + 5</gadget>
<output>8</output>

<gadget id="calculator">15 / 8</gadget>
<output>15/8 = around 1.875</output>

<result>B</result>
in an electric circuit, two resistors with resistances 3 ohm and 5 ohm are connected in parallel. in this case, if r is the combined resistance of these two resistors, then the reciprocal of r is equal to the sum of the reciprocals of two resistors. what is the value?
divide(multiply(3, 5), add(3, 5))
the wording is a bit confusing , though basically we are told that 1 / r = 1 / 3 + 1 / 5 , from which it follows that r = 15 / 8 ohms . answer : b .