BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Cant get this concept

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Sun Oct 13, 2013 8:43 am
[email protected] wrote:The sum of digits of integer z is 186 and z -10^n-4 what is the value of positive integer n
This question doesn't make any sense. Namely, the part in green.
Also, please make the exponents clear.
For example, 10^n-4 can be interpreted as EITHER (10^n)-4 OR 10^(n-4)

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Master | Next Rank: 500 Posts
Posts: 429
Joined: Wed Sep 19, 2012 11:38 pm
Thanked: 6 times
Followed by:4 members

by [email protected] » Sun Oct 13, 2013 9:02 am
Sorry for the typo it is the sum of the digits of integer z is 186 and z=(10^n)-4, what is the value of positive integer n

Brent@GMATPrepNow wrote:
[email protected] wrote:The sum of digits of integer z is 186 and z -10^n-4 what is the value of positive integer n
This question doesn't make any sense. Namely, the part in green.
Also, please make the exponents clear.
For example, 10^n-4 can be interpreted as EITHER (10^n)-4 OR 10^(n-4)

Cheers,
Brent
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Sun Oct 13, 2013 9:08 am
Please go back and edit the original post so that others see the correct question.

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Sun Oct 13, 2013 9:15 am
[email protected] wrote:The sum of the digits of integer z is 186 and z=(10^n)-4, what is the value of positive integer n
Since 10^n is a 1 followed by n zeros, we know that z = 999....996
So, how many 9's are there?

The sum of the digits of integer z is 186
So, 9+9+9+9+9+....+9+9+6 = 186
This means that 9+9+9+9+9+....+9+9 = 180
So, there must be 20 9's in the above sum.
So, z = 9999999....9996 (where there are twenty 9's and one 6)
In other words, z is a 21-digit number.
This means that 10^n must be a 22-digit number.
In other words, 10^n must be 1 followed by 21 zeros.
So, n = 21

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Post new topic Post Reply
• Page 1 of 1