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What is the probability that a three digit number is divis

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What is the probability that a three digit number is divis  [#permalink]

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New post Updated on: 12 Mar 2013, 01:33
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What is the probability that a three digit number is divisible by 7?

A. 1/7
B. 127/900
C. 32/225
D. 129/900
E. 1/8

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Originally posted by emmak on 12 Mar 2013, 00:39.
Last edited by Bunuel on 12 Mar 2013, 01:33, edited 1 time in total.
Edited the question.
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Re: What is the probability that a three digit number is divis  [#permalink]

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New post 12 Mar 2013, 04:34
1
4
emmak wrote:
What is the probability that a three digit number is divisible by 7?

A. 1/7
B. 127/900
C. 32/225
D. 129/900
E. 1/8


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Hope it helps.
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Re: What is the probability that a three digit number is divis  [#permalink]

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New post 12 Mar 2013, 02:56
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emmak wrote:
What is the probability that a three digit number is divisible by 7?

A. 1/7
B. 127/900
C. 32/225
D. 129/900
E. 1/8


Total 3 digit integers which are divisible by 7 :

(994-105)/7+1 = 128

The total number of 3 digit integers = (999-100)+1 = 900

The required probability : 128/900 = 32/225

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Re: What is the probability that a three digit number is divis  [#permalink]

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New post 24 Mar 2013, 21:31
rakeshd347 wrote:
vinaymimani wrote:
emmak wrote:
What is the probability that a three digit number is divisible by 7?

A. 1/7
B. 127/900
C. 32/225
D. 129/900
E. 1/8


Total 3 digit integers which are divisible by 7 :

(994-105)/7+1 = 128

The total number of 3 digit integers = (999-100)+1 = 900

The required probability : 128/900 = 32/225

C.

Hi Mate
How did you calculate the total number of 3 digit integers which are divisible by 7. Is there any shortcut for this.


Check here: how-many-multiples-of-4-are-there-between-12-and-94862.html#p730075

Hope it helps.
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Collection of Questions:
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Re: What is the probability that a three digit number is divis  [#permalink]

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New post 13 Feb 2016, 17:59
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emmak wrote:
What is the probability that a three digit number is divisible by 7?

A. 1/7
B. 127/900
C. 32/225
D. 129/900
E. 1/8


ok, total # of 3 digit numbers is: 9x10x10 or 900. we need to have a denominator that is multiple of 900. A is out right away.

now, let's see..105 is a multiple of 7. 994 is a multiple of seven. between, there will be 994/7 - 105/7 +1 multiples, or 128.
128/900 = 64/450 = 32/225

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Re: What is the probability that a three digit number is divis  [#permalink]

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New post 16 Feb 2016, 22:12
mau5 wrote:
emmak wrote:
What is the probability that a three digit number is divisible by 7?

A. 1/7
B. 127/900
C. 32/225
D. 129/900
E. 1/8



All 3 digit numbers are numbers from 100 to 999 or total 900 numbers [(999-100)+1]

In one set of 100, we have 14 multiples of 7 (14*7=98) Remember we are leaving the 2 left in each 100 for now.
or, in 9 sets of 100 we will have 9*14 =126 multiples of 7

in 9 sets of 100 those 2 left earlier will become 9*2 =18, we get two multiples of 7 from here.
Total multiples = 126 +2 = 128

Probability= 128/900 =64/450=32/225
Answer C
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Re: What is the probability that a three digit number is divis  [#permalink]

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New post 09 Jun 2018, 10:25
See we need to calculate the number of multiples of 7 which are 3 digit numbers and divide that by 900 which is the total amount of 3 digit numbers..So first we find the first multiple of 7 in a 3 digit world. i.e 105.... 7*15=105 and then find the last which is 994 as 7*142= 994.. So the number of multiples = 142-15+1= 128.. We add one as both 142 and 15 have to be included in counting the multiples.. We can also calculate this as 142-14( the number of multiples which are not 3 digit i.e 2 digit or 1 digit multiples.. ) 128/900 is the answer... i.e 32/225


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Re: What is the probability that a three digit number is divis &nbs [#permalink] 09 Jun 2018, 10:25
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