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If n is an integer between 10 and 99, is n < 80?

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If n is an integer between 10 and 99, is n < 80?  [#permalink]

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New post 15 Jan 2012, 23:49
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If n is an integer between 10 and 99, is n < 80?

(1) The sum of the two digits of n is a prime number.
(2) Each of the two digits of n is a prime number.

I know this must be easy. The answer is B (statement 2 is sufficient alone, while statement 1 is not). Doesn't that lead to tons of possible values of n?
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Re: If n is an integer between 10 and 99, is n < 80?  [#permalink]

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New post 16 Jan 2012, 03:25
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vandygrad11 wrote:
If n is an integer between 10 and 99, is n < 80?

(1) The sum of the two digits of n is a prime number.
(2) Each of the two digits of n is a prime number.

I know this must be easy. The answer is B (statement 2 is sufficient alone, while statement 1 is not). Doesn't that lead to tons of possible values of n?


If n is an integer between 10 and 99. Is n < 80?

Notice that n is an integer between 10 and 99 means that n is two-digit integer.

(1) The sum of the two digits of n is a prime number. Clearly insufficient: for example 83>80 and 38<80.

(2) Each of the two digits of n is a prime number --> greatest one digit prime is 7, thus max value of n is 77, which is less than 80. Sufficient.

Answer: B.

vandygrad11 wrote:
I am lost on this one. Prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23, etc. There are several values that satisfy the conditions of 10>n>80 while both digits are prime numbers, for instance 23, 32, 57, etc. Is that the reason that we can eliminate #2? Similarly, not to sound stupid, but is 67 then the only integer that meets the conditions of #1? Thanks.


We are told that n is a two-digit integer and each of these two digits is a prime, so n can be: 22, 23, 25, 27, ... and as greatest one digit prime is 7, thus max value of n is 77.

As what n could be taking in account statement (1):
23 --> 2+3=5=prime;
25 --> 2+5=7=prime;
29 --> 2+9=11=prime;
...

Hope it's clear.
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Re: If n is an integer between 10 and 99, is n < 80?  [#permalink]

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New post 16 Jan 2012, 00:28
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vandygrad11 wrote:
If n is an integer between 10 and 99, is n < 80?

(1) The sum of the two digits of n is a prime number.
(2) Each of the two digits of n is a prime number.

I know this must be easy. The answer is B (statement 2 is sufficient alone, while statement 1 is not). Doesn't that lead to tons of possible values of n?



1. let n be 67 then 6+7 = 13 (prime) and n < 80
but if n is 89 then 8+9 =17 (prime) and n >80. hence insuff

2. 8 and 9 are not prime so n < 80 as no value above 80 satisfies stmnt 2
hence suff

B
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Re: If n is an integer between 10 and 99, is n < 80?  [#permalink]

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New post 16 Jan 2012, 00:38
kp1811 wrote:
vandygrad11 wrote:
If n is an integer between 10 and 99, is n < 80?

(1) The sum of the two digits of n is a prime number.
(2) Each of the two digits of n is a prime number.

I know this must be easy. The answer is B (statement 2 is sufficient alone, while statement 1 is not). Doesn't that lead to tons of possible values of n?



1. let n be 67 then 6+7 = 13 (prime) and n < 80
but if n is 89 then 8+9 =17 (prime) and n >80. hence insuff

2. 8 and 9 are not prime so n < 80 as no value above 80 satisfies stmnt 2
hence suff

B


I am lost on this one. Prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23, etc. There are several values that satisfy the conditions of 10>n>80 while both digits are prime numbers, for instance 23, 32, 57, etc. Is that the reason that we can eliminate #2? Similarly, not to sound stupid, but is 67 then the only integer that meets the conditions of #1? Thanks.
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Re: If n is an integer between 10 and 99, is n < 80?  [#permalink]

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New post 16 Jan 2012, 03:21
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vandygrad11 wrote:
kp1811 wrote:
vandygrad11 wrote:
If n is an integer between 10 and 99, is n < 80?

(1) The sum of the two digits of n is a prime number.
(2) Each of the two digits of n is a prime number.

I know this must be easy. The answer is B (statement 2 is sufficient alone, while statement 1 is not). Doesn't that lead to tons of possible values of n?



1. let n be 67 then 6+7 = 13 (prime) and n < 80
but if n is 89 then 8+9 =17 (prime) and n >80. hence insuff

2. 8 and 9 are not prime so n < 80 as no value above 80 satisfies stmnt 2
hence suff

B


I am lost on this one. Prime numbers are 2, 3, 5, 7, 11, 13, 17, 19, 23, etc. There are several values that satisfy the conditions of 10>n>80 while both digits are prime numbers, for instance 23, 32, 57, etc. Is that the reason that we can eliminate #2? Similarly, not to sound stupid, but is 67 then the only integer that meets the conditions of #1? Thanks.


67 is not the only number for #1

we can have several numbers satisfying this condition like 23,32, 12, 21,43,34

also for stmnt 2 any number = or > than 80 will have 8 or 9 as ten's digit which are not prime and don't agree with stmnt 2
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Re: If n is an integer between 10 and 99. Is n < 80?  [#permalink]

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New post 26 Jan 2017, 06:22
(1) the sum of the digits is prime.

We can pick n=83, since 8+3=11 which is prime.

Is 83 < 80? No.

We can also pick 32, since 3+2=5 which is prime.

Is 32 < 80? Yes.

No and Yes, therefore insufficient.

(2) Each of the digits is prime.

Well, that means that each digit is either 2, 3, 5 or 7. In other words, the biggest possible value for n is 77. Therefore, every possible value for n will be less than 80: sufficient.

(1) is insufficient, (2) is sufficient: choose (b).
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If n is an integer between 10 and 99, is n < 80?  [#permalink]

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New post 11 Jul 2017, 07:54
geometric wrote:
If n is an integer between 10 and 99, is n < 80?

(1) The sum of the two digits of n is a prime number.
(2) Each of the two digits of n is a prime number.

I know this must be easy. The answer is B (statement 2 is sufficient alone, while statement 1 is not). Doesn't that lead to tons of possible values of n?



If n is an integer between 10 and 99, is n < 80?

(1) The sum of the two digits of n is a prime number.

Lets take numbers:

\(76 - 7 + 6 = 13 =\)Prime \(< 80\)

\(85 - 8 + 5 = 13 =\)Prime \(> 80\)

Hence, (1) ===== is NOT SUFFICIENT


(2) Each of the two digits of n is a prime number.

\(8\) & \(9\) are non prime numbers

Hence, the only possibility of having both the digits as prime is when the number is \(< 80\)

Hence, (2) ===== is SUFFICIENT


Hence, Answer is B


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Re: If n is an integer between 10 and 99, is n < 80?  [#permalink]

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