Today Rebecca is 34 years old

This topic has expert replies
Senior | Next Rank: 100 Posts
Posts: 93
Joined: Mon Apr 25, 2016 2:22 pm
Thanked: 1 times
Followed by:1 members

Today Rebecca is 34 years old

by boomgoesthegmat » Mon Apr 25, 2016 2:32 pm

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

Today Rebecca, who is 34 years old, and her daughter, who is 8 years old, celebrate their birthdays. How many years will pass before Rebecca's age is twice her daughter's age?
A) 10
B) 14
C) 18
D) 22
E) 26

Answer: C

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Mon Apr 25, 2016 3:54 pm
boomgoesthegmat wrote:Today Rebecca, who is 34 years old, and her daughter, who is 8 years old, celebrate their birthdays. How many years will pass before Rebecca's age is twice her daughter's age?
A) 10
B) 14
C) 18
D) 22
E) 26

Answer: C
I think the best (i.e., fastest) approach is to TEST the answer choices.
However, for those who prefer using algebra, here's an algebraic approach:

Let x be the number of years from today.
So, x years in the future, Rebecca's age will be 34 + x
And, x years in the future, her daughter's age will be 8 + x

We want Rebecca's future age to be twice her daughter's future age.
We can create the following "word equation": (Rebecca's future age) = 2(daughter's future age)
Or we can write: (34 + x) = 2(8 + x)
Expand to get: 34 + x = 16 + 2x
Solve to get: x = 18

Answer: C

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image

GMAT/MBA Expert

User avatar
Elite Legendary Member
Posts: 10392
Joined: Sun Jun 23, 2013 6:38 pm
Location: Palo Alto, CA
Thanked: 2867 times
Followed by:511 members
GMAT Score:800

by [email protected] » Mon Apr 25, 2016 4:07 pm
Hi boomgoesthegmat,

Certain questions in the Quant section can be solved rather easily by TESTing THE ANSWERS.

Here, we know that Rebecca's current age is 34 and her daughter's age is 8. We're asked how many years will need to pass by before Rebecca's age is exactly TWICE her daughter's age. Since the 5 answer choices are all numbers, we can TEST them until we find the match...

A) 10 years
Rebecca will be 44
Daughter will be 18
44 is NOT double 18

B) 14 years
Rebecca will be 48
Daughter will be 22
48 is NOT double 22

C) 18 years
Rebecca will be 52
Daughter will be 26
52 IS double 26
This must be the answer.

Final Answer: C

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

User avatar
Master | Next Rank: 500 Posts
Posts: 410
Joined: Fri Mar 13, 2015 3:36 am
Location: Worldwide
Thanked: 120 times
Followed by:8 members
GMAT Score:770

by OptimusPrep » Mon Apr 25, 2016 8:16 pm
boomgoesthegmat wrote:Today Rebecca, who is 34 years old, and her daughter, who is 8 years old, celebrate their birthdays. How many years will pass before Rebecca's age is twice her daughter's age?
A) 10
B) 14
C) 18
D) 22
E) 26

Answer: C
Testing values in an efficient way to solve this question, but in such problems, I always prefer going for equations rather that testing values.

Assume that Rebecca is twice her daughter's age after x years.
Hence we have, 34 + x = 2*(8 + x)
34 + x = 16 + 2x
x = 18

Correct Option: C

GMAT Instructor
Posts: 2630
Joined: Wed Sep 12, 2012 3:32 pm
Location: East Bay all the way
Thanked: 625 times
Followed by:119 members
GMAT Score:780

by Matt@VeritasPrep » Wed Apr 27, 2016 2:18 pm
Let's put it in words first, then assign variables.

Rebecca's Age + Some Number of Years = 2 * (Daughter's Age + Same Number of Years)

We know the two initial ages, and we can call the Number of Years y.

34 + y = 2 * (8 + y)

34 + y = 16 + 2y

18 = y

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 7223
Joined: Sat Apr 25, 2015 10:56 am
Location: Los Angeles, CA
Thanked: 43 times
Followed by:29 members

by Scott@TargetTestPrep » Thu Jan 04, 2018 8:53 am
boomgoesthegmat wrote:Today Rebecca, who is 34 years old, and her daughter, who is 8 years old, celebrate their birthdays. How many years will pass before Rebecca's age is twice her daughter's age?
A) 10
B) 14
C) 18
D) 22
E) 26
We are given that Rebecca is 34 and her daughter is 8. We can let n = the number of years before Rebecca is twice as old as her daughter. At that time, Rebecca will be (34 + n) years old and her daughter will be (8 + n) years old, and Rebecca will be twice her daughter's age:

34 + n = 2(8 + n)

34 + n = 16 + 2n

18 = n

Answer: C

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage