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

 It is currently 24 May 2019, 16:09

### 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

# 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: 55271
If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

04 Jan 2018, 23:47
00:00

Difficulty:

35% (medium)

Question Stats:

76% (02:02) correct 24% (02:06) wrong based on 57 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: 55271
Re: If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

04 Jan 2018, 23:48
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: 2759
If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

05 Jan 2018, 16:35
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

_________________
SC Butler has resumed!
Get two SC questions to practice, whose links you can find by date, here.
Intern
Joined: 12 Oct 2017
Posts: 41
Re: If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

05 Jan 2018, 20:05
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: 108
Re: If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

05 Jan 2018, 22:04
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: 63
Re: If Janice was 25 years old z years ago and Lisa will be 23 years old  [#permalink]

### Show Tags

06 Jan 2018, 05:40
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   [#permalink] 06 Jan 2018, 05:40
Display posts from previous: Sort by

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

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.