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

Redeem

Question of the Day - 27th August, 2009

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 74
Joined: Fri Jul 31, 2009 11:38 am
Thanked: 4 times
Followed by:1 members

Question of the Day - 27th August, 2009

by quant-master » Wed Aug 26, 2009 3:42 pm
Question 1:

How many five-digit numbers are there, if the two leftmost digits are even, the other digits are odd and the digit 4 cannot appear more than once in the number?
a)1875
b)2000
c)2375
d)2500
e)3875

Question 2:

6 persons seat themselves at round table. What is the probability that 2 given persons are adjacent?
(A) 1/5
(B) 2/5
(C) 1/10
(D) 1/7
(E) 2/15

OA will be posted in 24 hrs time

Thanks,
Quant-Master
https://gmat-quants.blocked - My Blog Updated almost daily with new quant fundas. Find collection of quants question in my blog
Top
Source: — Problem Solving |
User avatar
Master | Next Rank: 500 Posts
Posts: 157
Joined: Tue Oct 07, 2008 5:47 am
Thanked: 3 times

by PussInBoots » Wed Aug 26, 2009 4:59 pm
Q1:
1st digit: 4 possibilities
2nd digit: 5 possibilities (dont forget 0)
4th digit: 5 odd numbers, so 5 possibilities
3rd and 5th: 4 possibilities each

64 * 25 = 1600

Q2:
2/5. Could someone post explanation of the numeric solution, because I solved it my drawing table and fixing one of the choices?
Top
Master | Next Rank: 500 Posts
Posts: 268
Joined: Sat Aug 15, 2009 9:22 am
Thanked: 19 times
Followed by:1 members
GMAT Score:700

by capnx » Wed Aug 26, 2009 5:02 pm
1st Q:
One 4
1*4*5*5*5 = 500
3*1*5*5*5 = 375
No 4
3*4*5*5*5 = 1500
sum = 2375

2nd Q:
(2*4!)/5! = 2/5
Top
Legendary Member
Posts: 752
Joined: Sun May 17, 2009 11:04 pm
Location: Tokyo
Thanked: 81 times
GMAT Score:680

by tohellandback » Wed Aug 26, 2009 10:33 pm
Answer 1:
E-Even
O- ODD
Number is of the form EE OOO
no 4's
3*4*5*5*5=1500
One 4:
when 4 at first place:
4*5*5*5=500
when 4 at 2nd place:
3*5*5*5=375
total=2375
Answer C

Answer 2)
circular permutation:
total number ways of arranging 6 people in circular arrangement=5!
when two people are adjacent=4!*2
probability=4!*2/5!= 2/5
Answer B
Last edited by tohellandback on Thu Aug 27, 2009 2:16 am, edited 1 time in total.
The powers of two are bloody impolite!!
Top
Master | Next Rank: 500 Posts
Posts: 156
Joined: Sat Jul 19, 2008 6:41 am
Thanked: 8 times

My Answer

by enniguy » Thu Aug 27, 2009 1:31 am
Q 1. - E.
Expected format: EEOOO
With 4 as a possibility for first E (Then second E cannot be 4):-

4 * 4 * 5 * 5 * 5 = 16 * 125.

With 4 as a possibility for second E(Then first E cannot be 4):-

3 * 5 * 5 * 5 * 5 = 15 * 125.

Total = 31 * 125 = 1875.

Q 2. - B.
Number of ways of selecting 2 people out of 6:
6C2 = 15.

Imagine 6 people sitting on a round table. Then you will have 6 pairs of adjacent people sitting (Instead of 5 since this is a round table), Hence, total number of adjacent people "at a time" = 6

Probablity = 6 / 15 = 2/5.
Top
Post new topic Post Reply
• Page 1 of 1