GMAT prep old retired test

[sudaif]

If it is 6:27 in the evening on a certain day, what time in the morning was it exactly 2,880,717 minutes earlier? (Assume standard time in one location.)
(A) 6:22
(B) 6:24
(C) 6:27
(D) 6:30
(E) 6:32
OA is D
Now sure how to get there
I got to 6:24 answer B
If you start with 2,880,000 you end up back at 6:27 pm since 2,880,000 when divided by 60 gives us 48,000. And that constitutes 4,000 full 24 hour cycles or days. Then you're left with 717 minutes --- which is 3 less minutes than 60*12=720 minutes -- which means you fall short of the 6:27 mark by 3 minutes. I am probably complicating this question - but still would appreciate any input you can provide. thanks

[dinesh19aug]

It took me a while but I finally know why it is 6:30 PM.

You were correct upto the part that 48000 back it will be 6:27 PM.
Now you need to balance 717 minutes.

Solution:
At 6:27 PM number of minutes passed = (18Hr * 60) + 27 = 1107 minutes.

717 minutes before 1107 minutes = 1107 - 717 = 390 minutes.
So what is the time at 390 minutes => 390/60 = 6 Hr 30 mutes

It is 6:30 AM in the morning.

[sudaif]

Dinesh - i like your math solution. but i found it even easier to think of a clock. if i were to go back from 6:27 (counterclockwise) 717 minutes, I would essentially be going back 11 hours and 57 minutes. Thus, the time would fall short of the original time of 6:27 by 3 minutes. thus, when working counterclockwise on the clock...it would be 6:30.

[RonPurewal]

heh.

i have my doubts as to whether this is actually an official problem, but it admits a very nice and easy solution: just look at the last digit.

specifically:
the current time ends with a "7".
you're subtracting a number of minutes that also ends with a "7".
therefore, the answer must end with "0".
done.
(d).

how about that?