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

Redeem

Sum equal to 5

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
Senior | Next Rank: 100 Posts
Posts: 92
Joined: Thu Oct 06, 2011 8:06 am
Thanked: 18 times

by Neo Anderson » Mon Mar 12, 2012 8:47 am
that means a four digit number whose digits should sum up to 5:-
number containing: 2,1,1,1 => 4 such numbers
2,2,1,0 => 12 such numbers
3,1,1,0 => 12 such numbers
3,2,0,0 => 12 such numbers
4,1,0,0 => 12 such numbers
5,0,0,0 => 4 such numbers
thus total of 4+12+12+12+12+4 = 56 numbers with sun of digit =5 and number < 10,000[/u]
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Mon Mar 12, 2012 8:31 pm
rajatvmittal wrote:How many positive integers less than 10,000 are there in which sum of digits equals 5?

We need to find integers between 0 to 9999, in which the sum of digits adds up to 5.

(1) One digit is 5 and all other are 0: 0005, 0050, 0500, 5000 or we can say that no. of ways we can arrange the digits = 4!/3! = 4 ways
(2) Three 1's and one 2: 1112, this can be done in 4!/3! = 4 ways
(3) One 4 and one 1: 4100, this can be done in 4!/2! = 12 ways
(4) One 3 and one 2: 3200, this can be done in 4!/2! = 12 ways
(5) One 3 and two 1's: 3110, this can be done in 4!/2! = 12 ways
(6) Two 2's and One 1: 2210, this can be done in 4!/2! = 12 ways

Therefore, required number of positive integers = (12 * 4) + (4 * 2) = 48 + 8 = 56

The correct answer is C.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top
Post new topic Post Reply
• Page 1 of 1