A boy finds an average of 10 positive integers. Each

Oldest

Best Reply

Author

Message

TAGS:

Senior Manager

Joined: 30 Aug 2003

Posts: 348

Location: dallas , tx

Followers: 1

Kudos [?]: 2 [0], given: 0

A boy finds an average of 10 positive integers. Each [#permalink]

21 Dec 2003, 12:27

00:00

Question Stats:

0% (00:00) correct

0% (00:00) wrong

based on 0 sessions

A boy finds an average of 10 positive integers. Each integeres contain two digits .By mistake the boy interchanges the digits of one number say ba for ab. Due to this the average become 1.8 less than the previous one.What was the difference of the two digit a and b?
a)4
b)2
c)6
d)8

Any easy & understandable solution?
_________________

shubhangi

Joined: 13 Nov 2003

Posts: 1031

Location: Florida

Followers: 1

Kudos [?]: 5 [0], given: 0

[#permalink]

21 Dec 2003, 13:27

2 ??

here's how I did it..

suppose that the sum of 9 integers is A9
S is the average.

{A9+(10X+Y)}/10 = S

after intechanging digits;
{A9+(10Y+X)}/10 = S-1.8

subtract 2nd from 1st, u will get X-Y = 2

Intern

Joined: 04 Oct 2003

Posts: 42

Location: Silicon Valley, CA

Followers: 0

Kudos [?]: 1 [0], given: 0

[#permalink]

21 Dec 2003, 15:02

dj - exellent approach. Thanks for the solution.

CEO

Joined: 15 Aug 2003

Posts: 3549

Followers: 55

Kudos [?]: 627 [0], given: 781

Re: PS [#permalink]

22 Dec 2003, 12:44

shubhangi wrote:

let the number be represented by 10a + b
a = tens digits
b = unit digit
we know that.
Orginal Average - Mistaken Average = 1.8
[(Sum of 9 nos.) + (10 a+b) / 10] - [Sum of 9 nos +(10b +a) / 10]= 1.8

that is just...

[(10a + b ) - (10b +a)] /10 =1.8 ( 10 is the common denominator..so
we can simplify)
10a + b -10b -a = 18
9a - 9b =18

thus,
a- b =2

recall a = tenths digits, b =units digits

Answer B

Senior Manager

Joined: 30 Aug 2003

Posts: 348

Location: dallas , tx

Followers: 1

Kudos [?]: 2 [0], given: 0

[#permalink]

22 Dec 2003, 15:42

Yuppy!!
2 is right.
thanks both of you .. praet and dj.
_________________

shubhangi

[#permalink] 22 Dec 2003, 15:42

		Similar topics	Author	Replies	Last post
Similar Topics:		A student finds the average of 10 positive integers. Each	Praetorian	1	08 Oct 2003, 18:10
		Three positive integers: m. n and q, their average is 10,	blog	10	03 Feb 2008, 01:10
		If the average of positive integers x, y, and z is 10, what	arjtryarjtry	4	25 Jul 2008, 03:45
		If the average of 5 positive integers is 40 and the	nafishasan60	1	04 Feb 2012, 04:15
	6	S is a set of positive integers. The average of the terms in	rohitgarg	9	23 Sep 2012, 20:27

A boy finds an average of 10 positive integers. Each

Main navigation

GMAT Resources

Partners

MBA Resources

GMAT ® is a registered trademark of the Graduate Management Admission Council ® (GMAC ®). GMAT Club's website has not been reviewed or endorsed by GMAC.

GMAT Courses

Admissions Consulting

A boy finds an average of 10 positive integers. Each

A boy finds an average of 10 positive integers. Each

Main navigation

GMAT Resources

Partners

MBA Resources