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problem need help

by anwarma » Thu Jun 12, 2008 5:48 am
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%

ANS is D

I added the 3 +2 = 5 and then divided it by 24 hours. I am getting .208.
Can someone tell what am i doing wrong or is there easier way to do this.
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hey!

by ektamatta » Thu Jun 12, 2008 7:50 am
hey!

I just come up with approximate numbers

we have to add 3hr 45min+ 2 hr 55 min

so we will get 6 hr 40min...i m really bad in converting this whole thing in hr so

i just simply took 6hr/24x100= 25%

then i looked the answer choice..choice c is 24% that doesn't go with our answer so i came up with choice D which is 28%. If u can covert 6hr 40 min then u can get 28%. thats what i think
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by VP_Jim » Thu Jun 12, 2008 7:58 am
I think you're on the right track by rounding - you just rounded down when you should've rounded up.

If you do 3+2=5, you're ignorning the fact that it's actually 3:45 an 2:55, which are practically 4 hours and 3 hours, respectively. So rather than doing 3+2=5, I would do 4+3=7.

Then, just go 7/24 = 29%, which is close to 28%, so D is correct.
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by anwarma » Thu Jun 12, 2008 8:01 am
Thanks for the help.

I guess word approximation does not mean anything in this case :wink:

6 hrs and 40min converts to 6.66hrs, so divide 6.66 to 24, you get .2777
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by AleksandrM » Thu Jun 12, 2008 9:51 am
You could get the precise answer by simple converting 6 hours and 40 minutes into a fraction

20/3 and then used the percentage set-up to calculate:

20/3/24 = x/100

2000/3 = 24x or 2000 = 72x

250 = 9x

x = 27.7777 or about 28
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