Help, 2005-10-4 question 6-10

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2005-10-4 question 6-10:

Questions 6-11:

A lighting control panel has exactly seven switches, numbered from 1 to 7. Each switch is either in the on position or in the off position. The circuit load of the panel is the total number of its switches that are on. the control panel must be configured in accordance with the following conditions:

  If switch 1 is on, then switch 3 and switch 5 are off.

  If switch 4 is on, them switch 2 and switch 5 are off.

  The switch whose number corresponds to the circuit load of the panel is itself on. (这句话到底是什么意思？是不是说如果有四个开关是开的，那么开关4 也就是开的？)

 6. Which one ofthe following could be a complete and accurate list of the switches that are on?

 (A)  switch 2, switch  3, switch 4, switch 7

 (B)  switch 3 , switch 6, switch 7

 (C)  switch 2, switch 5, switch 6

  (D)  switch 1, switch 3, switch 4

  (E)  switch 1, switch 5

7.  If switch 1 and switch 3 are both off, then which one of the following could be two switches that are both on?

  (A)  switch 2 and switch 7

  (B)  switch 4 and switch 6

  (C)  swithc 4 and switch 7

  (D)  switch 5 and switch 6

  (E)  switch 6 and switch 7

就是比如有3盏灯亮，那么3号灯就亮。四盏灯亮，4号灯就亮。   

亮几盏灯，那么相对应的那个号码的灯就亮的。

有帮助否？

"The switch whose number corresponds to the circuit load of the panel is itself on. (这句话到底是什么意思？是不是说如果有四个开关是开的，那么开关4 也就是开的？)"

you are right in that.

proceed to the questions, and use Elimination strategy.

6. 1 on ->3,5 off  eliminate D, E; 4 on ->2,5 off  eliminate A;

choice C: since 2,5 on, 1, 4 must be off. The possible ON's could be 2,3,5,6 or 2,5,6. but both violate the rule of "The switch whose number corresponds to the circuit load of the panel is itself on."

so B is the right anwser.

7. I used elimination on Question 7 too. After tring all the combinations, only A is feasible.