Q9

[jamel.exhem]

how is this done?

[timmydoeslsat]

This is a question asking for the maximum circuit load number if 6 and 7 are both off. We are told in the prompt that the the circuit load number represents the total number of switches on, and that this number must always be on.

So we have seven numbers in this game.

ON ...... OFF
......... 6 7

We have five numbers left: 1 2 3 4 5

Could we fit all five in there? No. Due to these two rules we must always follow:

1 ---> ~3 and ~5
4 ---> ~2 and ~5

Could we fit exactly four numbers on? To do this, we must have switch #4 on, as we must have the circuit load number on. And if 4 is on, we would have 2 and 5 out, which would cause four variables to be out, which means we could never have four variables on.

Could we fit exactly three numbers on?

Sure, let's make it easy and not trigger those conditional rules at all! We can have 2, 3, and 5. 1 and 4 will be out and thus those rules are not even triggered.

Nonetheless, three is the maximum. We were from the largest number available in the answer choices and work our way down if necessary.