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Re: If a and b are positive integers, what is the value of a + b? [#permalink]

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30 Nov 2005, 11:15

Here is my explanation:

1) insuff, dont know what a or b are 8a=5b

2)insuff, this is saying that greatest common factor of a and b is 1
ex. 12 and 7 or any prime number pair ( ex. 2 and 5)

together

5/8= a/b : answers have to be multiples of the numberator and denominator. ex. 10 and 16 or 15 and 24. These answers have common factors. Since 5 and 8 are in its most simplified fraction form, it has to be the answer.

If you can explain it better please let us know. thanks

Re: If a and b are positive integers, what is the value of a + b? [#permalink]

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30 Nov 2005, 17:21

joemama142000 wrote:

If a and b are positive integers, what is the value of a + b? 1) a/b = 5/b 2) the greatest comon divisor of a and b is 1

make sure your OE follows your question.

joemama142000 wrote:

Here is my explanation: 1) insuff, dont know what a or b are 8a=5b 2)insuff, this is saying that greatest common factor of a and b is 1 ex. 12 and 7 or any prime number pair ( ex. 2 and 5) together 5/8= a/b: answers have to be multiples of the numberator and denominator. ex. 10 and 16 or 15 and 24. These answers have common factors. Since 5 and 8 are in its most simplified fraction form, it has to be the answer. If you can explain it better please let us know. thanks

Re: If a and b are positive integers, what is the value of a + b? [#permalink]

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30 Nov 2005, 17:34

Anyway, here is the original question and explanation. I thought it was tricky.

If a and b are positive integers, what is the value of a + b ?
(1) a/b=5/8
(2) The greatest common divisor of a and b is 1.

Here is my explanation:

1) insuff, dont know what a or b are 8a=5b

2)insuff, this is saying that greatest common factor of a and b is 1
ex. 12 and 7 or any prime number pair ( ex. 2 and 5)

together

5/8= a/b : answers have to be multiples of the numberator and denominator. ex. 10 and 16 or 15 and 24. These answers have common factors. Since 5 and 8 are in its most simplified fraction form, it has to be the answer.

Re: If a and b are positive integers, what is the value of a + b? [#permalink]

Show Tags

19 Jul 2011, 05:46

joemama142000 wrote:

Anyway, here is the original question and explanation. I thought it was tricky.

If a and b are positive integers, what is the value of a + b ? (1) a/b=5/8 (2) The greatest common divisor of a and b is 1.

Here is my explanation:

1) insuff, dont know what a or b are 8a=5b

2)insuff, this is saying that greatest common factor of a and b is 1 ex. 12 and 7 or any prime number pair ( ex. 2 and 5)

together

5/8= a/b : answers have to be multiples of the numberator and denominator. ex. 10 and 16 or 15 and 24. These answers have common factors. Since 5 and 8 are in its most simplified fraction form, it has to be the answer.

SORRY! if i'm asking a silly question...

since a/b = 5/8. why can't we just plug in a = 5 and b = 8? Pls explain. thanks!

Re: If a and b are positive integers, what is the value of a + b? [#permalink]

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21 Jul 2011, 06:18

1

This post received KUDOS

at miweekend...

consider a/b=5/8 if u consider some other number 25/40 and simplifying it would also get 5/8 so the value given might not ration not the original value
_________________

Regards, Harsha

Note: Give me kudos if my approach is right , else help me understand where i am missing.. I want to bell the GMAT Cat

Re: If a and b are positive integers, what is the value of a + b? [#permalink]

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22 Jul 2011, 00:33

miweekend wrote:

joemama142000 wrote:

Anyway, here is the original question and explanation. I thought it was tricky.

If a and b are positive integers, what is the value of a + b ? (1) a/b=5/8 (2) The greatest common divisor of a and b is 1.

Here is my explanation:

1) insuff, dont know what a or b are 8a=5b

2)insuff, this is saying that greatest common factor of a and b is 1 ex. 12 and 7 or any prime number pair ( ex. 2 and 5)

together

5/8= a/b : answers have to be multiples of the numberator and denominator. ex. 10 and 16 or 15 and 24. These answers have common factors. Since 5 and 8 are in its most simplified fraction form, it has to be the answer.

SORRY! if i'm asking a silly question...

since a/b = 5/8. why can't we just plug in a = 5 and b = 8? Pls explain. thanks!

thanks. good explanation indeed. never think of it...