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

 It is currently 10 Dec 2018, 05:09

### 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

## Events & Promotions

###### Events & Promotions in December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
• ### Free lesson on number properties

December 10, 2018

December 10, 2018

10:00 PM PST

11:00 PM PST

Practice the one most important Quant section - Integer properties, and rapidly improve your skills.
• ### Free GMAT Prep Hour

December 11, 2018

December 11, 2018

09:00 PM EST

10:00 PM EST

Strategies and techniques for approaching featured GMAT topics. December 11 at 9 PM EST.

# If Janice was 25 years old z years ago and Lisa will be 23 years old

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 51067
If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

04 Jan 2018, 22:47
00:00

Difficulty:

35% (medium)

Question Stats:

79% (02:02) correct 21% (02:17) wrong based on 48 sessions

### HideShow timer Statistics

If Janice was 25 years old z years ago and Lisa will be 23 years old in p years, what was the average (arithmetic mean) of their ages 5 years ago?

A. (48 + z - p)/2
B. (38 - z + p)/2
C. (38 + z + p)/2
D. (38 + z - p)/2
E. (48 + z + p)/2

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 51067
Re: If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

04 Jan 2018, 22:48
Bunuel wrote:
If Janice was 25 years old z years ago and Lisa will be 23 years old in p years, what was the average (arithmetic mean) of their ages 5 years ago?

A. (48 + z - p)/2
B. (38 - z + p)/2
C. (38 + z + p)/2
D. (38 + z - p)/2
E. (48 + z + p)/2

Check other Age Problems in our Special Questions Directory.
_________________
Senior SC Moderator
Joined: 22 May 2016
Posts: 2197
If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

05 Jan 2018, 15:35
1
Bunuel wrote:
If Janice was 25 years old z years ago and Lisa will be 23 years old in p years, what was the average (arithmetic mean) of their ages 5 years ago?

A. (48 + z - p)/2
B. (38 - z + p)/2
C. (38 + z + p)/2
D. (38 + z - p)/2
E. (48 + z + p)/2

Assign values that make the equations easy.
Let Janice = 30 now, z years ago she was 25
z = 5
Let Lisa = 20 now, in p years she will be 23
p = 3

Average of their ages 5 years ago? Five years ago
Janice: (30 - 5) = 25
Lisa: (20 - 5) = 15
Average 5 yrs ago $$\frac{25+15}{2}=20$$

All the answers are divided by 2.
With z = 5, p = 3, find the answer with a numerator of 40, because 40/2 = 20 = average of their ages

A. (48 + z - p)/2
48 + 5 - 3 = 50 NOT A MATCH

B. (38 - z + p)/2
38 - 5 + 3 = 36 NOT A MATCH

C. (38 + z + p)/2
38 + 5 + 3 = 46 NOT A MATCH

D. (38 + z - p)/2
38 + 5 - 3 = 40 MATCH

E. (48 + z + p)/2
48 + 5 + 3 = 56 NOT A MATCH

Intern
Joined: 12 Oct 2017
Posts: 40
Re: If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

05 Jan 2018, 19:05
If Janice was 25 years old z years ago => Janice's age now = 25 + z => 5years ago = 25+ z - 5
Lisa will be 23 years old in p years => Lisa's age now = 23 - p => 5 years ago = 23 - p - 5
Hence, the average (arithmetic mean) of their ages 5 years ago = (25+z-5 + 23-p -5)/2 = (38 + z - p)/2. the answer is D
-----
Please +1 kudos if the explanation is clear.
Thank you!
Manager
Joined: 22 May 2015
Posts: 103
Re: If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

05 Jan 2018, 21:04
Straight forward classic algebra problem.

Assume present ages are j and p
Eq 1 : 25 = j-z
Eq 2 : 23 = l+p

Need to find avg of there ages 5 years ago ie (j-5+l-5) / 2 = (j+l-10)/2
substituting j and l from eq 1 and eq 2 we get the answer as D
_________________

Consistency is the Key

Manager
Joined: 23 Oct 2017
Posts: 64
Re: If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

06 Jan 2018, 04:40
Bunuel wrote:
If Janice was 25 years old z years ago and Lisa will be 23 years old in p years, what was the average (arithmetic mean) of their ages 5 years ago?

A. (48 + z - p)/2
B. (38 - z + p)/2
C. (38 + z + p)/2
D. (38 + z - p)/2
E. (48 + z + p)/2

------------
Janice's age z years ago = 25 years old, so as of now age of janice = 25 +z
Since Lisa will be 23 years old in p years, so as of now age of lisa = 23- p
Now average of both their 5 years beack will be:
(25+z-5 + 23-p -5)/2
= (38 + z - p)/2
Re: If Janice was 25 years old z years ago and Lisa will be 23 years old &nbs [#permalink] 06 Jan 2018, 04:40
Display posts from previous: Sort by