GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 14 Dec 2019, 12:30

GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

The two digits in Jack's age are the same as the digits in Bill's age,

Author Message
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 59725
The two digits in Jack's age are the same as the digits in Bill's age,  [#permalink]

Show Tags

22 Mar 2019, 00:28
00:00

Difficulty:

35% (medium)

Question Stats:

73% (02:48) correct 27% (03:01) wrong based on 15 sessions

HideShow timer Statistics

The two digits in Jack's age are the same as the digits in Bill's age, but in reverse order. In five years Jack will be twice as old as Bill will be then. What is the difference in their current ages?

(A) 9
(B) 18
(C) 27
(D) 36
(E) 45

_________________
GMAT Club Legend
Joined: 18 Aug 2017
Posts: 5483
Location: India
Concentration: Sustainability, Marketing
GPA: 4
WE: Marketing (Energy and Utilities)
Re: The two digits in Jack's age are the same as the digits in Bill's age,  [#permalink]

Show Tags

22 Mar 2019, 03:52
1
Bunuel wrote:
The two digits in Jack's age are the same as the digits in Bill's age, but in reverse order. In five years Jack will be twice as old as Bill will be then. What is the difference in their current ages?

(A) 9
(B) 18
(C) 27
(D) 36
(E) 45

Jack age = 10a+b
Bill= 10b+a
5 years later
(10a+b)+5 = 2*(10b+a+5)
we get
8a= 19b+5
b=1
a=3
so age 31 & 13
difference = 18
IMO B
Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 8701
Location: United States (CA)
Re: The two digits in Jack's age are the same as the digits in Bill's age,  [#permalink]

Show Tags

24 Mar 2019, 18:44
Bunuel wrote:
The two digits in Jack's age are the same as the digits in Bill's age, but in reverse order. In five years Jack will be twice as old as Bill will be then. What is the difference in their current ages?

(A) 9
(B) 18
(C) 27
(D) 36
(E) 45

We can let Jack’s age = 10A + B and Bill’s age = 10B + A. (Notice that since Jack is the older of the two, A > B.) Since in 5 years Jack will be twice as old as Bill:

10A + B + 5 = 2(10B + A + 5)

10A + B + 5 = 20B + 2A + 10

8A - 19B = 5

8A = 19B + 5

A = (19B + 5)/8

We see that B has to be odd, otherwise A won’t be an integer. Therefore, if B = 1, then A = 24/8 = 3. So Jack can be 31 years and Bill can be 13 years and their age difference is 18 years.

_________________

Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com
122 Reviews

5-star rated online GMAT quant
self study course

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

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

Re: The two digits in Jack's age are the same as the digits in Bill's age,   [#permalink] 24 Mar 2019, 18:44
Display posts from previous: Sort by