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# Number System!!

Author Message
Senior Manager
Joined: 16 Feb 2011
Posts: 259
Followers: 4

Kudos [?]: 162 [0], given: 9

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26 Aug 2011, 11:50
00:00

Difficulty:

(N/A)

Question Stats:

50% (00:00) correct 50% (00:02) wrong based on 2 sessions

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How many integers between 234700 and 458600 have tens digit 1 and units digit 3?

how to solve such questions within 2 min timeframe??
Senior Manager
Joined: 16 Feb 2011
Posts: 259
Followers: 4

Kudos [?]: 162 [0], given: 9

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26 Aug 2011, 12:36
Indeed it is..pls help me with the explanation part..
Senior Manager
Joined: 03 Mar 2010
Posts: 440
Schools: Simon '16 (M)
Followers: 5

Kudos [?]: 304 [1] , given: 22

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26 Aug 2011, 14:11
1
KUDOS
DeeptiM wrote:
Indeed it is..pls help me with the explanation part..

Surely.
Take 234700 and 234800. Now how many numbers are there between them? 100.
How many numbers are there between them such that there is 1 at ten's place and 3 at unit's place. 1. 234713.
Take 234700 and 234900.
how many numbers are there between them? 200.
How many numbers are there between them such that there is 1 at ten's place and 3 at unit's place. 2. 234713 and 234813.
Take 234700 and 234500.
how many numbers are there between them? 300.
How many numbers are there between them such that there is 1 at ten's place and 3 at unit's place. 3. 234713, 234813 and 234913.

By now you must have realized the pattern here. For every hundred there is one such number.
Subtract 458600 and 234700
458600-234700=223900
For every hundred 1 such number
So for 223900 there will be 2239 such numbers.

Also, please include answer options and OA in your question. And yes if this forum/post is helpful to you, show appreciation. ( You know how!)
_________________

My dad once said to me: Son, nothing succeeds like success.

Director
Joined: 01 Feb 2011
Posts: 755
Followers: 14

Kudos [?]: 124 [0], given: 42

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26 Aug 2011, 18:12
-13 appears once in every hundred

458600-234700 = 123900 => 1239 hundreds

so in 1239 hundred's , there are 1239 such numbers with 1 in ten's digit and 3 in units digit.

Director
Joined: 03 May 2007
Posts: 875
Schools: University of Chicago, Wharton School
Followers: 6

Kudos [?]: 209 [0], given: 7

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26 Aug 2011, 18:24
DeeptiM wrote:
How many integers between 234700 and 458600 have tens digit 1 and units digit 3?

how to solve such questions within 2 min timeframe??

The desired numbers have a position of xxx,x13 i.e. every hundred has such a number.

= (458,600 - 234,700)/100
= 223900/100
= 2239

It even does not take more than 20 second.
Manager
Joined: 09 Jun 2011
Posts: 104
Followers: 0

Kudos [?]: 51 [0], given: 0

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01 Sep 2011, 22:16
The desired numbers have a position of xxx,x13 i.e. every hundred has such a number.

= (458,600 - 234,700)/100
= 223900/100
= 2239
For every hundred 1 such number

So for 223900 there will be 2239 such numbers.

I loved this explanation.
Re: Number System!!   [#permalink] 01 Sep 2011, 22:16
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