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

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

P & C

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 40
Joined: Sat Jan 30, 2010 10:38 am
by vijaynarayanan » Thu Jul 01, 2010 6:02 am
Question: A company plans to assign identification numbers to its employees. Each number is to consist of 4 different digits from 0 to 9, inclusive, except that the 1st digit cannot be 0. How many different identification numbers are possible?

I feel that the answer should be 9x10x10x10=9000.

But I see that the answer is 4536. Can someone explain how?

Thx
Vijay.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
User avatar
Legendary Member
Posts: 1893
Joined: Sun May 30, 2010 11:48 pmFollowed by: 7 members
Thanked: 215 times

by kvcpk » Thu Jul 01, 2010 6:27 am
vijaynarayanan wrote:Question: A company plans to assign identification numbers to its employees. Each number is to consist of 4 different digits from 0 to 9, inclusive, except that the 1st digit cannot be 0. How many different identification numbers are possible?

I feel that the answer should be 9x10x10x10=9000.

But I see that the answer is 4536. Can someone explain how?

Thx
Vijay.
Hi Vijay,

First place can be filled by 9 digits 1 to 9
second by 9 [because, we cannot repaet the first digit]
third by 8 [cant repeat 1 and 2 digits ]
fourth by 7

so total 9*9*8*7 = 4536
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 294
Joined: Wed May 05, 2010 4:01 am
Location: india
Thanked: 57 times

by amising6 » Thu Jul 01, 2010 6:58 am
vijaynarayanan wrote:Question: A company plans to assign identification numbers to its employees. Each number is to consist of 4 different digits from 0 to 9, inclusive, except that the 1st digit cannot be 0. How many different identification numbers are possible?

I feel that the answer should be 9x10x10x10=9000.
if you take

But I see that the answer is 4536. Can someone explain how?

Thx
Vijay.
good question
your reasoning makes sense because we are not talking about non repeatation
as for example 1111 and 2222 are all unique
Ideation without execution is delusion
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1