A museum ran a security system stress test continuously before

Question

A museum ran a security system stress test continuously before shutting it down. On what day of the week did the museum shut down the test?

(1) If the museum had continued the test for another 6 hours, the test would have ended on Monday.
(2) If the museum had shut down the test 17 hours earlier than it actually did, the test would have ended on Monday

M47-82

Bunuel · Accepted Answer

GMAT Club Official Solution:

A museum ran a security system stress test continuously before shutting it down. On what day of the week did the museum shut down the test?

(1) If the museum had continued the test for another 6 hours, the test would have ended on Monday.

If adding 6 hours would make the shutdown day Monday, then the actual shutdown must be sometime from Sunday 18:00 up to Monday 18:00. So the shutdown day could be Sunday or Monday. Not sufficient.

(2) If the museum had shut down the test 17 hours earlier than it actually did, the test would have ended on Monday.

If shifting the shutdown 17 hours earlier would make the shutdown day Monday, then the actual shutdown must be sometime from Monday 17:00 up to Tuesday 17:00. So the shutdown day could be Monday or Tuesday. Not sufficient.

(1)+(2) The shutdown time must satisfy both ranges, so it must be from Monday 17:00 up to Monday 18:00. That means the shutdown day must be Monday. Sufficient.

Or: from (1) we have that the shutdown day could be Sunday or Monday, and from (2) we have that the shutdown day could be Monday or Tuesday. To satisfy both, the shutdown must be on Monday. Sufficient.

Answer: C.

thisisakr · Answer

So this question is slightly tricky I feel

1: if the test ran for 6 hrs more it would end on Monday

Now it could be that the best ended at 10pm on Sunday so 6 hrs more and it ended on 3 am on Monday 
However it could also be that the test ended on 3 pm Monday then 6 hrs more would be 9pm and it would still be Monday

So we can’t really tell if the test ended on Sunday or Monday .  Insufficient

2: similar reasoning as statement 1 ——  Insufficient

Together , The condition becomes that the test has to end on Monday by ensuring the before and after time

now let see if the test ended on Monday at 5:50 pm or 17:50 hrs on Monday

Then 6hrs more would be 11:50 pm / 23:50 pm on Monday 
And 17hrs earlier would be 12:50 am / 00:50 am on Monday

Hence, we can say the test ended on Monday —  Sufficient  (C)

Note if we took Sunday as the end of test day then it gets eliminated bcz of statement 2
And if you take Tuesday as end of test day then it gets eliminated bcz of statement 1

Adit_ · Answer

Statement 1:
Clearly INSUFFICIENT. As the day could be Sunday or Monday itself.

Statement 2:
INSUFFICIENT.
Because the day could be the next day = Tuesday or it could be Monday itself as 17hrs is still way smaller than 24 hrs.

Combining the two:
Now if you combine both the front and backward counting it adds up to 23 hrs. It now means that there is only 1 hr time frame between which the stress test is shut down and since both statements happen on a Monday the day of the week is on Monday in that 1 hr gap which is 5pm to 6pm in this case.
SUFFICIENT.

Answer:  Option C

A museum ran a security system stress test continuously before

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A museum ran a security system stress test continuously before

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