m1-#18 : Retired Discussions [Locked]
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# m1-#18

Author Message
Senior Manager
Joined: 17 May 2010
Posts: 299
GMAT 1: 710 Q47 V40
Followers: 4

Kudos [?]: 48 [0], given: 7

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18 Jul 2011, 14:17
How many of the three-digit numbers are divisible by 7?

105
106
127
128
142

Explanation Given:
-----------------------
Approach One: Divide all of the three-digit numbers $$999 - 100 + 1 = 900$$ (Don't forget to add 1 to get the number of all the 3-digit numbers) by 7, which is 128.57, and then round it off to 128.
-----------------------
My question: When you round 128.57 shouldn't it result in 129? In this case in the answer choices there was no 129, but what if on the D-Day there is 129? What would you do then?
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Senior Manager
Joined: 24 Mar 2011
Posts: 457
Location: Texas
Followers: 5

Kudos [?]: 166 [0], given: 20

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18 Jul 2011, 20:28
You have a valid question, i dont know.

But i would solve it this way -
1st 3 digit # divisible by 7 is 105

and last is 994

now 994 = 105+(n-1)7
==> n =128 which is choice D.
Current Student
Joined: 26 May 2005
Posts: 565
Followers: 18

Kudos [?]: 203 [0], given: 13

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18 Jul 2011, 20:31
gijoedude wrote:
How many of the three-digit numbers are divisible by 7?

105
106
127
128
142

Explanation Given:
-----------------------
Approach One: Divide all of the three-digit numbers $$999 - 100 + 1 = 900$$ (Don't forget to add 1 to get the number of all the 3-digit numbers) by 7, which is 128.57, and then round it off to 128.
-----------------------
My question: When you round 128.57 shouldn't it result in 129? In this case in the answer choices there was no 129, but what if on the D-Day there is 129? What would you do then?

You cannot usee 999 and 100, because those are not multiples of 7. u have to choose the smallest 3 digit multiple of 7 and highest 3-digit multiple;

105..............................994

(994-105)/7 +1
=127+1= 128
Senior Manager
Joined: 17 May 2010
Posts: 299
GMAT 1: 710 Q47 V40
Followers: 4

Kudos [?]: 48 [0], given: 7

### Show Tags

19 Jul 2011, 17:39
sudhir18n wrote:
gijoedude wrote:
How many of the three-digit numbers are divisible by 7?

105
106
127
128
142

Explanation Given:
-----------------------
Approach One: Divide all of the three-digit numbers $$999 - 100 + 1 = 900$$ (Don't forget to add 1 to get the number of all the 3-digit numbers) by 7, which is 128.57, and then round it off to 128.
-----------------------
My question: When you round 128.57 shouldn't it result in 129? In this case in the answer choices there was no 129, but what if on the D-Day there is 129? What would you do then?

You cannot usee 999 and 100, because those are not multiples of 7. u have to choose the smallest 3 digit multiple of 7 and highest 3-digit multiple;

105..............................994

(994-105)/7 +1
=127+1= 128

What I posted was actually from the explanation given on the test, not what I used.
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Re: m1-#18   [#permalink] 19 Jul 2011, 17:39
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# m1-#18

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