OG #119

This topic has expert replies
Junior | Next Rank: 30 Posts
Posts: 12
Joined: 03 Dec 2012

OG #119

by shivshankar054 » Mon Apr 08, 2013 8:00 am

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

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

User avatar
Senior | Next Rank: 100 Posts
Posts: 37
Joined: 16 Dec 2009
Location: New York & Rotterdam
Thanked: 9 times
GMAT Score:780

by misterholmes » Mon Apr 08, 2013 8:08 am
This solution is in the OG. What's your question?

Kind Regards,

Misterholmes
www.gmatdojo.com
Mindfulness, Concentration, Insight

User avatar
GMAT Instructor
Posts: 15533
Joined: 25 May 2010
Location: New York, NY
Thanked: 13060 times
Followed by:1901 members
GMAT Score:790

by GMATGuruNY » 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.

The correct answer is B.

For two similar problems, check here:

https://www.beatthegmat.com/ratios-fract ... 15365.html
Mitch Hunt
Private Tutor for the GMAT and GRE
[email protected]

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

Available for tutoring in NYC and long-distance.
For more information, please email me at [email protected].
Student Review #1
Student Review #2
Student Review #3

User avatar
GMAT Instructor
Posts: 15533
Joined: 25 May 2010
Location: New York, NY
Thanked: 13060 times
Followed by:1901 members
GMAT Score:790

by GMATGuruNY » 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.

Answer choice B: 16 days
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!

The correct answer is B.
Mitch Hunt
Private Tutor for the GMAT and GRE
[email protected]

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

Available for tutoring in NYC and long-distance.
For more information, please email me at [email protected].
Student Review #1
Student Review #2
Student Review #3

User avatar
Senior | Next Rank: 100 Posts
Posts: 37
Joined: 16 Dec 2009
Location: New York & Rotterdam
Thanked: 9 times
GMAT Score:780

by misterholmes » Mon Apr 08, 2013 8:22 am
Well ok then! I submit a third solution, based on the number of days D.
The plan was to read 90*D pages, but instead of that we read 75*(D-6) pages and then had 690 pages left.
So 90*D=75*D+240
And D=16

Kind Regards,

Misterholmes
www.gmatdojo.com
Mindfulness, Concentration, Insight

Junior | Next Rank: 30 Posts
Posts: 12
Joined: 03 Dec 2012

by shivshankar054 » Mon Apr 08, 2013 9:05 am
Thank you very much!!

GMAT/MBA Expert

User avatar
Elite Legendary Member
Posts: 10392
Joined: 23 Jun 2013
Location: Palo Alto, CA
Thanked: 2867 times
Followed by:508 members
GMAT Score:800

Re: OG #119

by [email protected] » Sat Apr 24, 2021 7:47 pm
Hi All,

We’re told that Terry originally planned to read 90 pages/day to complete a particular reading assignment. However, she was only able to read 75 pages/day at first (for a certain number of days), which left her 690 pages that had to be read in the last 6 days of that original timeframe. We’re asked for the TOTAL number of days needed to complete all of the reading.

The Arithmetic that this question is based on can be approached in a number of different ways – and you can actually use a ‘comparison’ to get to the final answer fairly quickly.

Since the original plan was to read 90 pages/day, the last 6 days of reading was supposed to be (6)(90) = 540 pages. Terry had to actually read 690 pages though – which is 690 – 540 = 150 more pages than she had originally planned to read during those final days.

The difference between the original rate (re: 90 pages/day) and the amount she actually read early-on (75 pages/day) is 90 – 75 = 15 pages/day. This is interesting since she needed to make up 150 pages at the end (and 150 is 10 times 15). This means that she was reading at that slower rate for the first 10 days of reading – and she had to make up the amount that she ‘fell behind’ during the final 6 days.

That’s 10 + 6 = 16 total days of reading.

Final Answer: B

GMAT Assassins aren’t born, they’re made,
Rich
Contact Rich at [email protected]
Image