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GGUY
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately Updated on: 28 Nov 2014, 05:17
Originally posted by GGUY on 15 Jan 2008, 14:52.
Last edited by Bunuel on 28 Nov 2014, 05:17, edited 1 time in total.
Renamed the topic, edited the question, added the OA and moved to PS forum.
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D
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82% (01:36) correct 18% (01:43) wrong based on 762 sessions

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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately what percent of a day?

(A) 14%
(B) 16%
(C) 24%
(D) 28%
(E) 72%
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D
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 15 Jan 2008, 15:03
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D

30-sec way.

3h45+2h55= 5h(45+55)=5h(1h40)=6h40

100%*6h40/24h is between ~6*4/100~24% and ~7*4/100~28%
6h40 is closer to 7, therefore, D
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 15 Jan 2008, 15:13
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depends what you prefer...

i did it fairly quickly by converting 6hours 40mins to 400 mins. A quick multiplication in my head 24*6 yielded 144 ( since 12x12 = 144). So that told me a day had 1440 mins (approx 1500 to make it easier). 400 * 4 = 1600. so 400 is 25% of 1600, so it has to be a little over 25% of 1440. i.e 28%
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 15 Jan 2008, 19:23
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Since the question is asking for an approximate percentage

3:45+2:55 ~ 7 hours

% of day = 7*100/24 ~ 7*100/25= 28%

Answer is D.

If you had 27 and 29 as options you would probably need to do more accurate calculations. In this particular case while approximating values we increase both numerator and denominator so our calculations should be close
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 15 Jan 2008, 20:10
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Although I did it the way buffdaddy mentioned, I think the method that Travel09 mentioned would be the fastest.
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 15 Jan 2008, 22:46
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GGUY
I discovered that doing the math is a time consuming effort, reflecting on my overall speed in the test. Attached a Q from GMAT Paper Test 48, a very simple one.
Anyway, I'd appreciate a method to do the arithmetics quickly.

The sum of 3 hours 45 minutes and 2 hours 55
minutes is approximately what percent of a day?

(A) 14%
(B) 16%
(C) 24%
(D) 28%
(E) 72%

OA will follow.

5 hrs and 55+45 minutes 6 hrs and 40 mintues --> 6 2/3 hr/24 --> 6/24 --> 1/4 so u know its going to be greater than 25%. Therfore only answer is D.

Or u can do 20/3/24 --> 20/72 -> 10/36 --> 5/18 ~28%.
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 16 Jan 2008, 01:13
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GGUY
I discovered that doing the math is a time consuming effort, reflecting on my overall speed in the test. Attached a Q from GMAT Paper Test 48, a very simple one.
Anyway, I'd appreciate a method to do the arithmetics quickly.

The sum of 3 hours 45 minutes and 2 hours 55
minutes is approximately what percent of a day?

(A) 14%
(B) 16%
(C) 24%
(D) 28%
(E) 72%

OA will follow.

put everithing in minutes: 400/1440 equals 3 hours 45 minutes plus 2 hours 55. divide per 24*60 mins a day. therefore, simplify and obtain 250/9 which is somewhat less than 28.
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 16 Jan 2008, 05:51
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GGUY
I discovered that doing the math is a time consuming effort, reflecting on my overall speed in the test. Attached a Q from GMAT Paper Test 48, a very simple one.
Anyway, I'd appreciate a method to do the arithmetics quickly.

The sum of 3 hours 45 minutes and 2 hours 55
minutes is approximately what percent of a day?

(A) 14%
(B) 16%
(C) 24%
(D) 28%
(E) 72%

OA will follow.

Call 2 hours 55 minutes 3 hours. and round 3 hours 45 minutes down to 3 hours. Add them up and you get 6 hours. 24/6 = 1/4 but we rounded out 40 minutes, so the answer will be slightly higher than 25%. D is the only one that fits the bill. All in your head in a few seconds
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 17 Jan 2008, 03:20
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eschn3am
Call 2 hours 55 minutes 3 hours. and round 3 hours 45 minutes down to 3 hours. Add them up and you get 6 hours. 24/6 = 1/4 but we rounded out 40 minutes, so the answer will be slightly higher than 25%. D is the only one that fits the bill. All in your head in a few seconds
eschn3am, thanks. does that mean you look at the answers before you solve?
Travel09
Since the question is asking for an approximate percentage

3:45+2:55 ~ 7 hours

% of day = 7*100/24 ~ 7*100/25= 28%

Answer is D.

If you had 27 and 29 as options you would probably need to do more accurate calculations. In this particular case while approximating values we increase both numerator and denominator so our calculations should be close
I chose this one for me.

thanks all, each one got a kodus for his\hers efforts :lol:
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 17 Jan 2008, 05:57
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I actually run it through like this to get a ballpark number right off the bat. Then I look at the numbers. If there's only one possible answer that works I choose it and go on. If the answers are more detailed (which rarely happens with these types of problem) I'll go back and try a more mathematical approach.
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 02 Dec 2019, 03:54
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3H 45M and 2H 55M

adds up to 6H 40M


6H /24H = 25%

so our answer should be little over 25%

28% is the best fit for this question.
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 09 Aug 2021, 19:49
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Add the two times to get 6 hours and 40 mins. 40 mins is 2/3 of an hour. 6.67/24 is the answer. 6*4=24 so 6.67/24 is a little more than 25%.

D is the only answer that is a little more than 25%
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 09 Aug 2021, 21:51
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Sum is 6 hours 40 minutes: 6 * 60 + 40 = 400 minutes

In 1 day: 24 hours = 24 * 60 minutes

Percent: \(\frac{400 }{ 24} * 60 * 100 = 28%\)

Answer D
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 09 Aug 2021, 21:54
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Sum is 6 hours 40 minutes: 6 * 60 + 40 = 400 minutes

In 1 day: 24 hours = 24 * 60 minutes

Percent: \(\frac{400 }{ 24} * 60 * 100 = 28%\)

Answer D
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The sum of 3 hours 45 minutes and 2 hours 55 minutes is approximately 21 Oct 2022, 17:03
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eschn3am
GGUY
I discovered that doing the math is a time consuming effort, reflecting on my overall speed in the test. Attached a Q from GMAT Paper Test 48, a very simple one.
Anyway, I'd appreciate a method to do the arithmetics quickly.

The sum of 3 hours 45 minutes and 2 hours 55
minutes is approximately what percent of a day?

(A) 14%
(B) 16%
(C) 24%
(D) 28%
(E) 72%

OA will follow.

Call 2 hours 55 minutes 3 hours. and round 3 hours 45 minutes down to 3 hours. Add them up and you get 6 hours. 24/6 = 1/4 but we rounded out 40 minutes, so the answer will be slightly higher than 25%. D is the only one that fits the bill. All in your head in a few seconds

Yes, perfect solution. It's an important timesaving habit to use the answer choices to your advantage. When we notice that the question says "approximately", rounding and estimation are especially useful.
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