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Intern
Joined: 09 May 2017
Posts: 2

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21 Nov 2017, 17:33
1
VeritasPrepKarishma wrote:
CoffeeCreamSugar wrote:
Dara ran on a treadmill that had a readout indicating the time remaining in her exercise session. When the readout indicated 24 min 18 sec, she had completed 10% of her exercise session. The readout indicated which of the following when she had completed 40% of her exercise session?

A. 10 min 48 sec
B. 14 min 52 sec
C. 14 min 58 sec
D. 16 min 6 sec
E. 16 min 12 sec

Do a more efficient single calculation:

24 min 18 sec is 90% of her exercise time.
When she completes 40% of her exercise session, the readout will indicate 60% of the time.

So we need $$\frac{6}{9} * 24(\frac{18}{60}) = \frac{81}{5} = 16 ( \frac{1}{5}) = 16 (\frac{12}{60}) =$$16 min 12 sec

*Edited a calculation error.

Hi. Could you please explain the reasoning behind the last part? How did get to the 81/5?
Manager
Joined: 03 May 2017
Posts: 78

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21 Nov 2017, 20:19
1
CoffeeCreamSugar wrote:
Dara ran on a treadmill that had a readout indicating the time remaining in her exercise session. When the readout indicated 24 min 18 sec, she had completed 10% of her exercise session. The readout indicated which of the following when she had completed 40% of her exercise session?

A. 10 min 48 sec
B. 14 min 52 sec
C. 14 min 58 sec
D. 16 min 6 sec
E. 16 min 12 sec

$$Mental:$$

$$90 percent$$ = $$24 min 18 sec$$

$$60 percent$$ = $$\frac{2}{3} * 24 min 18 sec$$

= $$16 min 12 sec$$, i.e $$\frac{2}{3}$$ of each of $$24$$ and $$18$$ respectively

Hence, E.
Intern
Joined: 12 Oct 2017
Posts: 34

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27 Nov 2017, 23:27
When the readout indicated 24 min 18 sec, she had completed 10% of her exercise session.
=> 24 min 18 sec = total time for Daran to complete 90% of her excercise session.
=> total time to complete = 24min18 sec : 90% = 27 mins.
When she completes 40% of her exercise => timer should show the time remaining for 60% of her exercise = 60% * 27 mins = 16 min 20 sec
Intern
Joined: 02 Dec 2016
Posts: 5

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20 Sep 2018, 07:35
hacker wrote:
This problem can be done mentally without any calculations

Readout indicated 24 min 18 sec when she had completed 10% of her exercise.

This means remaining 90% of the work will take 24 min 18 sec => 30% will take 8 min 6 sec

so 40% completed i.e. 60% remaining of the work will take (24min 18 sec- 8 min 6 sec)= 16min 12 sec.

extremely elegant!
Manager
Joined: 14 Nov 2018
Posts: 88
Location: United Arab Emirates
Concentration: Finance, Strategy
Schools: LBS '22 (I)
GMAT 1: 590 Q42 V30
GMAT 2: 670 Q46 V36
GPA: 2.6

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19 Nov 2019, 04:11
Key is to recognize this is a proportion question - 90% is given need to calculate 60%

0.9=24.3min
0.6=x?

x=24.3*0.6/0.9
x=243*6/9=162

162 divide by 10=16.2 or 16 min 12 sec

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