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

 It is currently 25 Mar 2019, 23:25

### 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 2^x*7^y = z, what is the value of z ? (1) x − y = 1 (2) 2^x = 8

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 53832
If 2^x*7^y = z, what is the value of z ? (1) x − y = 1 (2) 2^x = 8  [#permalink]

### Show Tags

05 Mar 2019, 04:50
00:00

Difficulty:

15% (low)

Question Stats:

100% (00:59) correct 0% (00:00) wrong based on 24 sessions

### HideShow timer Statistics

If $$2^x*7^y = z$$, what is the value of z ?

(1) $$x − y = 1$$

(2) $$2^x = 8$$

_________________
VP
Joined: 31 Oct 2013
Posts: 1273
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
If 2^x*7^y = z, what is the value of z ? (1) x − y = 1 (2) 2^x = 8  [#permalink]

### Show Tags

05 Mar 2019, 05:20
Bunuel wrote:
If $$2^x*7^y = z$$, what is the value of z ?

(1) $$x − y = 1$$

(2) $$2^x = 8$$

Statement 1: x - y = 1. x=y + 1.

$$2^{y + 1} 7^y = z$$

$$2^y * 7^y*2 = z$$

$$(14)^y 2 = z.$$

No information about y. NOT sufficient.

Statement 2: $$2^x = 8$$. $$2^x = 2^3$$. x =3. No information about y. NOT sufficient.

Combining :

x - y = 1

3 - y = 1

y = 2.

So, x = 3 and y = 2. Now we can find out the total value.

SVP
Joined: 18 Aug 2017
Posts: 2497
Location: India
Concentration: Sustainability, Marketing
GPA: 4
WE: Marketing (Energy and Utilities)
Re: If 2^x*7^y = z, what is the value of z ? (1) x − y = 1 (2) 2^x = 8  [#permalink]

### Show Tags

05 Mar 2019, 11:02
Bunuel wrote:
If $$2^x*7^y = z$$, what is the value of z ?

(1) $$x − y = 1$$

(2) $$2^x = 8$$

#1
x-y=1
means x & y are consective values . but x & y are not know in suffieint
#2
2^x=8
or say x = 3
in sufficeint as y not know
so 1&2
x=3 and y = 2
sufficient
IMO C
_________________
If you liked my solution then please give Kudos. Kudos encourage active discussions.
Re: If 2^x*7^y = z, what is the value of z ? (1) x − y = 1 (2) 2^x = 8   [#permalink] 05 Mar 2019, 11:02
Display posts from previous: Sort by