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Offical Guide Question 64 (consecuitve Integers!)

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Offical Guide Question 64 (consecuitve Integers!)

by ela10rb » Sat Mar 09, 2013 7:33 am
How many integers are there between, but not including, integers r and s?

1) s-r=10
2) There are 9, integers between, but not including, r+1 and s+1


I am having trouble understanding that we assume above to be consecutive integers (however question does not mention it explicitly). Please could someone help me understand?
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by hemant_rajput » Sat Mar 09, 2013 8:04 am
ela10rb wrote:How many integers are there between, but not including, integers r and s?

1) s-r=10
2) There are 9, integers between, but not including, r+1 and s+1


I am having trouble understanding that we assume above to be consecutive integers (however question does not mention it explicitly). Please could someone help me understand?

I think you didn't understand question properly. Question is asking how many integers are there between r and s? We don't know about r and s, they could integers or not. Also we don't need to count them, so it doesn't matter if they are integer or not.

Lets take integer values for r and s, say 5 and 15 resp.

5,6,7,8,9,10,11,12,13,14,15

now there are 9 integers.

now lest take some non integer value for r and s.

5.5,6,7,8,9,10,11,12,13,14,15.2 - We need to find integer values, that is why I listed only integer values between 5.5 and 15.2 .


You need to find the count of integer not integer values itself, so there is not question to think in the manner you are doing.

Hope this helps.
I'm no expert, just trying to work on my skills. If I've made any mistakes please bear with me.
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by amandeep.hora » Sat Mar 09, 2013 8:19 am
How many integers are there between, but not including, integers r and s?

1) s-r=10
2) There are 9, integers between, but not including, r+1 and s+1


As the question is asking us to count the number of integers between 2 integers r and s and the wording "including" , it has to be a consecutive integers problem.

then it's extremely easy to solve
total no of integers between r and s including r and s = s-r + 1
Total no of integers excluding both r and s = s - r -1
total no of integers including anyone but not both = s-r

so statement 1 gives s-r =10 , it is sufficient to answer the question
Statement 2 gives s+1 -(r+1) = 9 again sufficient to answer the question
hence answer has to be D

Hope that helps !
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Aman
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by amandeep.hora » Sat Mar 09, 2013 8:20 am
How many integers are there between, but not including, integers r and s?

1) s-r=10
2) There are 9, integers between, but not including, r+1 and s+1


As the question is asking us to count the number of integers between 2 integers r and s and the wording "including" , it has to be a consecutive integers problem.

then it's extremely easy to solve
total no of integers between r and s including r and s = s-r + 1
Total no of integers excluding both r and s = s - r -1
total no of integers including anyone but not both = s-r

so statement 1 gives s-r =10 , it is sufficient to answer the question
Statement 2 gives s+1 -(r+1) = 9 again sufficient to answer the question
hence answer has to be D

Hope that helps !
Regards
Aman
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