MGMAT- VICS PS

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 » Sat May 14, 2011 1:43 am

Mr. and Mrs. Wiley have a child every J years. Their oldest child is now Tyears old. If
they have a child 2 years from now, how many children will they-have in total?
(A) {(T+2)/J} +1 (B)JT+1 (C)J/T + T/J (D)TJ-1 (E) (J+T)/J

anyone with algebraic approach for this ?

oa[spoiler]=a[/spoiler]

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 | Sat May 14, 2011 1:43 am

manpsingh87: Master | Next Rank: 500 Posts; Posts: 436; Joined: Tue Feb 08, 2011 3:07 amFollowed by: 6 members; Thanked: 72 times

by manpsingh87 » Sat May 14, 2011 3:45 am

bblast wrote:Mr. and Mrs. Wiley have a child every J years. Their oldest child is now Tyears old. If
they have a child 2 years from now, how many children will they-have in total?
(A) {(T+2)/J} +1 (B)JT+1 (C)J/T + T/J (D)TJ-1 (E) (J+T)/J

anyone with algebraic approach for this ?

oa[spoiler]=a[/spoiler]

here j is the difference in years after which mr. and mrs. wiley will have kid;
lets assume that difference is 2; and after 6 years, no. of kids born will be (6/2)+1; to understand why i add "1" consider the following diagram..!!
k1--2yr---k2--2yr---k3--2yr---k4; kid born in the 0th yr{i.e. the year from which counting starts,(reference year for other kids)} was not covered when we divide 6/2 hence we will have to add 1 in the expression,

now consider the scenario given in the question;

age of the eldest son is T years; after 2 years; gap of j years will be fulfilled and the couple wil have a new child; therefore age of eldest son after two year will be (T+2) and total no. of kids will be {T+2/j}+1; hence A

O Excellence... my search for you is on... you can be far.. but not beyond my reach!

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 » Sat May 14, 2011 4:35 am

bblast wrote:Mr. and Mrs. Wiley have a child every J years. Their oldest child is now Tyears old. If
they have a child 2 years from now, how many children will they-have in total?
(A) {(T+2)/J} +1 (B)JT+1 (C)J/T + T/J (D)TJ-1 (E) (J+T)/J

anyone with algebraic approach for this ?

oa[spoiler]=a[/spoiler]

I would plug in values.

Let J=2.
Let 2000 = year in which the first child is born.
Let now = 2006.
Since a child is born every 2 years, there are now 4 children -- born in 2000, 2002, 2004 and 2006 -- and the oldest age is T=6.
When a child is born 2 years from now, the number of children = 5. This is our target.

Now we plug J=2 and T=6 into the answers to see which yields our target of 5.

Only answer choice A works:
(T+2)/J + 1 = (6+2)/2 + 1 = 5.

The correct answer is A.

To solve algebraically:

Since the ages are all J years apart, they are evenly spaced integers.

Number of evenly spaced integers = (biggest - smallest)/(distance between each successive pair) + 1.

Biggest = T+2 (the age of the oldest child 2 years from now)
Smallest = 0 (the age of the last child at its birth 2 years from now)
Distance between each successive pair = J.

Number of children = (T+2 - 0)/J + 1 = (T+2)/J + 1.

Last edited by GMATGuruNY on Sat May 14, 2011 8:52 am, edited 2 times in total.

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

GMAT/MBA Expert

Whitney Garner: GMAT Instructor; Posts: 273; Joined: Tue Sep 21, 2010 5:37 amFollowed by: 74 members; Location: Durham, NC; Thanked: 154 times; GMAT Score:770

by Whitney Garner » Sat May 14, 2011 5:33 am

bblast wrote:Mr. and Mrs. Wiley have a child every J years. Their oldest child is now Tyears old. If
they have a child 2 years from now, how many children will they-have in total?
(A) {(T+2)/J} +1 (B)JT+1 (C)J/T + T/J (D)TJ-1 (E) (J+T)/J

anyone with algebraic approach for this ?

oa[spoiler]=a[/spoiler]

If you are interested in the "Algebraic Approach" I would definitely recommend utilizing a "Hybrid" approach: pick numbers just to understand the relationship, and then convert back to the algebra so you do not need to test all the answer choices.

Let's pretend that the Wiley's oldest is 10. That means that they have been having kids for 10 years. They will have 1 more child in 2 years - total number of years having kids = 10 + 2 = (T+2) = 12.

Ok, if we now say they have had kids every 4 years, they would have had the 12 year old, an 8 year old, a 4 year old and then the newest kid. The intuition would be to divide 12/3, but we forget that we are starting and ending with a kid (0, 4, 8, 12) so it is similar to finding the number of terms in a list (Most-Least + ONE). So this is like taking the total number of years the Wiley's had kids, dividing by the interval of the kids, then adding one for the newest arrival!

(T+2)/J + 1

Whit

Whitney Garner
GMAT/GRE/EA Instructor & Anxiety/Accommodations Coach
www.whitneygarner.com

Contributor to Beat The GMAT!

Math is a lot like love - a simple idea that can easily get complicated

Like this post

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

by bblast » Sat May 14, 2011 8:42 am

all three approaches to this good gmat problem covered. thank you experts.

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 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