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## OG #119

This topic has 2 expert replies and 3 member replies
shivshankar054 Junior | Next Rank: 30 Posts
Joined
03 Dec 2012
Posted:
12 messages

#### OG #119

Mon Apr 08, 2013 8:00 am
In order to complete a reading assignment on time, Terry planned to read 90 pages per day.However,she read only 75 pages per day at first, leaving 690 pages to be read during the last 6 days before the assignment was to be completed. How many days in all Terry have to complete the assignment on time?

A.15
B.16
C.25
D.40
E.46

shivshankar054 Junior | Next Rank: 30 Posts
Joined
03 Dec 2012
Posted:
12 messages
Mon Apr 08, 2013 9:05 am
Thank you very much!!

misterholmes Senior | Next Rank: 100 Posts
Joined
16 Dec 2009
Posted:
37 messages
9
Test Date:
November 2009
GMAT Score:
780
Mon Apr 08, 2013 8:22 am
Well ok then! I submit a third solution, based on the number of days D.
So 90*D=75*D+240
And D=16

Kind Regards,

Misterholmes

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misterholmes Senior | Next Rank: 100 Posts
Joined
16 Dec 2009
Posted:
37 messages
9
Test Date:
November 2009
GMAT Score:
780
Mon Apr 08, 2013 8:08 am
This solution is in the OG. What's your question?

Kind Regards,

Misterholmes

_________________
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### GMAT/MBA Expert

GMATGuruNY GMAT Instructor
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Mon Apr 08, 2013 8:17 am
shivshankar054 wrote:
In order to complete a reading assignment on time, Terry planned to read 90 pages per day.However,she read only 75 pages per day at first, leaving 690 pages to be read during the last 6 days before the assignment was to be completed. How many days in all Terry have to complete the assignment on time?

A.15
B.16
C.25
D.40
E.46
This is a weighted average/mixture question.

First set of days: Average number of pages per day = 75.
Last 6 days: Average number of pages per day = 690/6 = 115.
Mixture of the two sets of days: Average number of pages per day = 90.

Let F = the first set of days and L = the last 6 days.
To determine the ratio of F to L in the mixture, use ALLIGATION:

Step 1: Plot the 3 averages on a number line, with the averages for the two ingredients on the ends and the mixture average in the middle.
F 75-----------------90----------------115 L

Step 2: Calculate the distances between the averages.
F 75--------15-------90--------25------115 L

Step 3: Determine the ratio in the mixture.
The required ratio of F to L is the RECIPROCAL of the distances in red.
F:L = 25:15 = 5:3.

Since the actual value of L is 6 days, and F:L = 5:3 = 10:6, F = 10 and L = 6.
Thus, the total number of days = F+L = 10+6 = 16.

For two similar problems, check here:

http://www.beatthegmat.com/ratios-fraction-problem-t115365.html

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### GMAT/MBA Expert

GMATGuruNY GMAT Instructor
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Posted:
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Mon Apr 08, 2013 8:18 am
wied81 wrote:
From OG #119 - Problem solving:

119) In order to complete a reading assignment on time, Terry planned to read 90 pages per day. However, she read only 75 pages per day at first, leaving 690 pages to be read during the last 6 days before the assignment was to be completed. How many days in all did Terry have to complete the assignment on time?

A) 15

B) 16

C) 25

D) 40

E) 46

OA: B
An alternate approach is to plug in the answers, which represent the total number of days.
Since the planned rate was 90 pages per day, the total number of pages must be a multiple of 10.
Over the last 6 days, the total number of pages read = 690.
Thus, the total number of pages read at a rate of 75 pages per day must be a multiple of 10.
Answer choice A (15 days) implies 9 days at 75 pages per day.
Answer choice C (25 days) implies 19 days at 75 pages per day.
Neither of these answers will yield a total number of pages that is a multiple of 10.
Eliminate A and C.

10 days at 75 pages per day + 690 pages over the last 6 days = 10*75 + 690 = 1440.
16 days at 90 pages per day = 16*90 = 1440.
Success!

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GMATGuruNY@gmail.com
If you find one of my posts helpful, please take a moment to click on the "UPVOTE" icon.
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