The reason the answer to the Uni Challenge question is 12/13 and not 13/12 is because the "resistors in parallel" formula is "One over total resistance equals the Sum of (one over individual resistances)".
Well crikey arjay that move the goalposts. Was a voltage given to calculate current in amps or was the question about the total resistance of parallel resistors in ohms?
It was about total resistance of parallel resistors, yeah. I got it wrong as I rushed in my head and thought 1/4 = 1/6, giving an answer of 12/11 ... whoops.
If those values were resistance given in ohms. Then the three resistors in parallel would give an overall resistance of .11107 ohms. A parallel circuit of resistors always has a lower resistance than the lowest individual resistor in the circuit.
Jim the original post made no mention of parallel resistors or the massive fact that the fractions were reciprocals. 2,3 and 4 ohms would have been easy. Also fractions were rarely used in electronics but we got there. Haha.
Dont you find a common denominator.
Like 2, 3 and 4 will go into 12. So you get the answer in 12ths. 2 into 12 goes 6 = 6/12. 3 into 12 goes 4= 4/12. 4 into 12 goes 3 = 3/12. Then add the 12ths up 6/12+4/12+3/12= 13/12 which is 1 and 1/12.
So the answer is 1 1/12