MGMAT- VICS problem

Expert replies

bblast: Legendary Member; Posts: 1077; Joined: Mon Dec 13, 2010 1:44 amFollowed by: 33 members; Thanked: 118 times; GMAT Score:710

by bblast » Wed May 11, 2011 10:27 pm

Jake was 4.5 feet tall on his 12th birthday, when he began to have a growth
spurt. Between his 12th and 15th birthdays, he grew at a constant rate. If Jake
was 20% taller on his 15th birthday than on his 13th birthday, how many inches
per year did Jake grow during his growth spurt? (12 inches = 1 foot)

[spoiler]ans-6inches/year.[/spoiler]

I made a mistake in this question that I started this way.
12th birthday - P0 * k
13th birthday - P0 * k^2
14th birthday - P0 * k^3
15th birthday - P0 * k^4

given 15th-13th = 20%.

But obviously this question aint saying that the height increased by the same factor everyyear? how do i identify that this is a linear growth problem ? just because height cant grow exponentially ?

experts...

Cheers !!

Quant 47-Striving for 50
Verbal 34-Striving for 40

My gmat journey :
https://www.beatthegmat.com/710-bblast-s ... 90735.html
My take on the GMAT RC :
https://www.beatthegmat.com/ways-to-bbla ... 90808.html
How to prepare before your MBA:
https://www.youtube.com/watch?v=upz46D7 ... TWBZF14TKW_

Like this post

Source: Beat The GMAT — Problem Solving | Wed May 11, 2011 10:27 pm

vineeshp: Legendary Member; Posts: 965; Joined: Thu Jan 28, 2010 12:52 amFollowed by: 34 members; Thanked: 156 times; GMAT Score:720

by vineeshp » Wed May 11, 2011 10:46 pm

If the height grows exponentially, the question would mention it explicitly.

he grew at a constant rate: This directly means his growth was linear.

Last edited by vineeshp on Wed May 11, 2011 10:55 pm, edited 1 time in total.

Vineesh,
Just telling you what I know and think. I am not the expert.

Like this post

GMAT/MBA Expert

Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Wed May 11, 2011 10:51 pm

bblast wrote:Jake was 4.5 feet tall on his 12th birthday, when he began to have a growth
spurt. Between his 12th and 15th birthdays, he grew at a constant rate. If Jake
was 20% taller on his 15th birthday than on his 13th birthday, how many inches
per year did Jake grow during his growth spurt? (12 inches = 1 foot)

[spoiler]ans-6inches/year.[/spoiler]

I made a mistake in this question that I started this way.
12th birthday - P0 * k
13th birthday - P0 * k^2
14th birthday - P0 * k^3
15th birthday - P0 * k^4

given 15th-13th = 20%.

But obviously this question aint saying that the height increased by the same factor everyyear? how do i identify that this is a linear growth problem ? just because height cant grow exponentially ?

experts...

Solution:
A constant rate of change is anything that increases or decreases by the same amount for every trial. The question says that "Between his 12th and 15th birthdays, he grew at a constant rate". That means the increase is same every year.
Let the increase every year be 'i' feet.
So, on 13th birthday he is 4.5 + i feet.
On fourteenth birthday he is 4.5 + 2i feet and on 15th birthday he is 4.5 + 3i feet.
Now 1.2*(4.5 + i) = 4.5 + 3i.
Or 5.4 + 1.2i = 4.5 + 3i.
Or .9 = 1.8i
Or i = 0.5 feet = 6 inches.

Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/

Like this post

GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Wed May 11, 2011 11:29 pm

bblast wrote:Jake was 4.5 feet tall on his 12th birthday, when he began to have a growth
spurt. Between his 12th and 15th birthdays, he grew at a constant rate. If Jake
was 20% taller on his 15th birthday than on his 13th birthday, how many inches
per year did Jake grow during his growth spurt? (12 inches = 1 foot)

[spoiler]ans-6inches/year.[/spoiler]

I made a mistake in this question that I started this way.
12th birthday - P0 * k
13th birthday - P0 * k^2
14th birthday - P0 * k^3
15th birthday - P0 * k^4

given 15th-13th = 20%.

But obviously this question aint saying that the height increased by the same factor everyyear? how do i identify that this is a linear growth problem ? just because height cant grow exponentially ?

experts...

Initial height = 4.5* 12 = 54 inches.

On the GMAT we could plug in the answers, which would represent the growth per year.

Answer choice: 6 inches per year
At 13, Jake would be 54+6 = 60 inches.
At 15, Jake would be 60 + 2*6 = 72 inches.
72-60=12.
Since 12 =.2*60, success!

The correct answer is 6 inches per year.

Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

563 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (563 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review