this question is really ****ing me up, I've tried doing it SO many times using LCM and stuff but can't seem to get the right answer :
part a) A christmas tree has been decorated with a set of lights thatcontain two circuits. On each individual circuit, all the lights come and go off at the same time, but the two circuits are out of sync. Circuit 1: lights ON for 4 seconds, and OFF for 9 seconds.Circuit 2: lights ON for 7 seconds and OFF for 2 seconds,20 seconds ago, both sets of lights came ON at exactly the same time. In how many seconds from now will both sets of lights go OFF at the same time ?
part b) consider the same christmas tree as above but with the following circuits: Circuit 1: Lights ON for 3 seconds, OFF for 5 secondsCircuit 2: lights ON for 2 seconds, OFF for 6 seconds Ten seconds ago, both sets of lights went ON at exactly the same time. In how many seconds from now will both sets of lights go ON at the same time?
answers below, I just don't know how to get to them :