in an electric circuit , two resistors with resistances x and y are connected in parallel . if r is the combined resistance of these two resistors , then the reciprocal of r is equal to the sum of the reciprocals of x and y . what is r if x is 4 ohms and y is 5 ohms ?
"1 / r = 1 / x + 1 / y 1 / r = 1 / 4 + 1 / 5 = 9 / 20 r = 20 / 9 the answer is b ."
divide(multiply(5, 4), add(4, 5))