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How many number of times will the digit 7' be written when

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Director
Joined: 06 Sep 2006
Posts: 745
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How many number of times will the digit 7' be written when [#permalink]  06 Oct 2006, 21:03
How many number of times will the digit â€˜7' be written when listing the integers from 1 to 1000? (1) 271 (2) 300 (3) 252 (4) 304
Manager
Joined: 19 Aug 2006
Posts: 222
Followers: 1

Kudos [?]: 16 [0], given: 0

ANS: B) 300

From 0-99 , total No of '7' equal to- 20
Now consider from
000-99 =20
100-199=20
200-299=20
300-399=20
400-499=20
500-599=20
600-699=20
700-799=100+20 ( Hundredth digit 100 + regular 20 like from 0 to 99)
800-899=20
900-999=20
Total-------------
300
Senior Manager
Joined: 11 Jul 2006
Posts: 383
Location: TX
Followers: 1

Kudos [?]: 6 [0], given: 0

No of Ocurrences in Units = 10 * 10 =100 (7,17,27..97)
No if occurences in Tenths = 10 * 10 = 100 ( 70 , 71 , 72 ... , 79 )
No of occurences in hundreds = 1 * 100 = 100 (700,701, .... , 799)

Total = 300
GMAT Instructor
Joined: 04 Jul 2006
Posts: 1266
Followers: 24

Kudos [?]: 167 [0], given: 0

Re: Count of Number '7' [#permalink]  07 Oct 2006, 22:23
asaf wrote:
How many number of times will the digit â€˜7' be written when listing the integers from 1 to 1000? (1) 271 (2) 300 (3) 252 (4) 304

How many integers have one 7? 3*9*9= 243
How many integers have two 7s? 3*9=27
How many integers have three 7s? 1

Total= 243+2*27+3*1=243+54+3=300
Senior Manager
Joined: 28 Aug 2006
Posts: 302
Followers: 10

Kudos [?]: 99 [0], given: 0

ivymba wrote:
No of Ocurrences in Units = 10 * 10 =100 (7,17,27..97)
No if occurences in Tenths = 10 * 10 = 100 ( 70 , 71 , 72 ... , 79 )
No of occurences in hundreds = 1 * 100 = 100 (700,701, .... , 799)

Total = 300

yes always count this way........ no confusion and quicker

It must be 300
_________________
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