Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 26 Apr 2015, 23:24

### 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 June
Open Detailed Calendar

# If (3)^x - (3)^x-1 = 162, then x(x-1) =? a)12 b)16 c)20 d)30

Author Message
TAGS:
Manager
Joined: 13 Mar 2007
Posts: 98
Followers: 1

Kudos [?]: 11 [0], given: 0

If (3)^x - (3)^x-1 = 162, then x(x-1) =? a)12 b)16 c)20 d)30 [#permalink]  21 Apr 2007, 14:33
If (3)^x - (3)^x-1 = 162, then x(x-1) =?

a)12
b)16
c)20
d)30
e)81
Senior Manager
Joined: 12 Mar 2006
Posts: 367
Schools: Kellogg School of Management
Followers: 2

Kudos [?]: 36 [0], given: 3

3^x - 3^(x-1) = 162

=> 3^(x-1) * ( 3 - 1) = 162

=> 3^(x-1) = 81

=> x-1 = 4

=> x*(x-1) = 20

so C
Senior Manager
Joined: 01 Jan 2007
Posts: 326
Followers: 1

Kudos [?]: 17 [0], given: 0

GMAT_700 wrote:
If (3)^x - (3)^x-1 = 162, then x(x-1) =?

a)12
b)16
c)20
d)30
e)81

3^(x-1)[3-1]=162

3^(x-1)=81=3^4.

Comparing the powers of 3 we get x-1=4. Therefore x=5. And hence x(x-1)=4*5=20.

Javed.

Cheers!
Manager
Joined: 28 Feb 2007
Posts: 198
Location: California
Followers: 2

Kudos [?]: 6 [0], given: 0

GMAT_700 wrote:
If (3)^x - (3)^x-1 = 162, then x(x-1) =?

a)12
b)16
c)20
d)30
e)81

3^(x-1) {3 - 1} = 162
or 3 ^(x-1) = 81 = 3^4
or x - 1 = 4
so x = 5
x(x-1) = 20
Similar topics Replies Last post
Similar
Topics:
1 If 3 x - 3 x-1 = 162 , then x(x-1)= 4 23 Apr 2008, 04:11
If 3^x - 3^x-1 ,then x(x-1) = ? 1. 12 2. 16 3. 20 4. 30 5. 2 04 Feb 2008, 14:09
3^x - 3^x-1 = 162, what is x(x-1)? Ans: 20 4 15 Jul 2006, 17:45
3^x - 3^x-1 = 162, x (x - 1) = ? For some reason I'm stumped 5 09 Jul 2006, 11:16
If 3^x - 3^(x-1) = 162, then x(x-1)= a. 12 b. 16 c. 20 d. 30 8 19 Apr 2006, 20:47
Display posts from previous: Sort by