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# Is mp greater than m?

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Is mp greater than m? [#permalink]  10 Oct 2012, 10:09
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Is mp greater than m?

(1) m > p > 0
(2) p is less than 1

Hello experts,

Could anyone please explain how to approach this problem algebraically. As detailed an explanation as possible will be greatly appreciated. I was trying to understand the following.

a. I am clear on getting the first set of roots based on the information given in the stem. i.e mp-m>o --> m(p-1)>0. So m>0 and P>1. But didn't understand the reasoning behind obtaining the second set of roots by flipping the signs.
b. Also need help on understanding how to use the obtained roots in conjunction with options (1) and (2).
[Reveal] Spoiler: OA

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Re: Is mp greater than m? [#permalink]  10 Oct 2012, 10:19
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Is mp greater than m?

Question: is $$mp>m$$?

(1) m > p > 0. Since given that $$m>0$$, then we can reduce by positive $$m$$ and the question becomes: is $$p>1$$? We know that $$p>0$$, but that's not enough. Not sufficient.

(2) p is less than 1. No info about $$m$$. Not sufficient.

(1)+(2) From (1) the question became: "is $$p>1$$?" and (2) says that $$p<1$$, so we have definite NO answer to the question. Sufficient.

Hope it's clear.
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Re: Is mp greater than m? [#permalink]  10 Oct 2012, 10:22
1
KUDOS
GetThisDone wrote:
Is mp greater than m?

(1) m > p > 0
(2) p is less than 1

Hello experts,

Could anyone please explain how to approach this problem algebraically. As detailed an explanation as possible will be greatly appreciated. I was trying to understand the following.

a. I am clear on getting the first set of roots based on the information given in the stem. i.e mp-m>o --> m(p-1)>0. So m>0 and P>1. But didn't understand the reasoning behind obtaining the second set of roots by flipping the signs.
b. Also need help on understanding how to use the obtained roots in conjunction with options (1) and (2).

The question can be rephrased as "Is $$mp-m>0$$ or $$m(p-1)>0,$$ which is the same as asking whether $$m$$ and $$p-1$$ have the same sign?"

(1) Not sufficient. In order to know the sign of $$p-1$$ we have to know whether $$p$$ is greater or less than $$1.$$
(2) Not sufficient. We know nothing about $$m.$$

(1) and (2): Now we know for sure that both $$m$$ and $$p-1$$ are positive.
Sufficient.

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Love GMAT Quant questions and running.

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Re: Is mp greater than m? [#permalink]  10 Oct 2012, 10:24
1
KUDOS
Expert's post
EvaJager wrote:
GetThisDone wrote:
Is mp greater than m?

(1) m > p > 0
(2) p is less than 1

Hello experts,

Could anyone please explain how to approach this problem algebraically. As detailed an explanation as possible will be greatly appreciated. I was trying to understand the following.

a. I am clear on getting the first set of roots based on the information given in the stem. i.e mp-m>o --> m(p-1)>0. So m>0 and P>1. But didn't understand the reasoning behind obtaining the second set of roots by flipping the signs.
b. Also need help on understanding how to use the obtained roots in conjunction with options (1) and (2).

The question can be rephrased as "Is $$mp-m>0$$ or $$m(p-1)>0,$$ which is the same as asking whether $$m$$ and $$p-1$$ have the same sign?"

(1) Not sufficient. In order to know the sign of $$p-1$$ we have to know whether $$p$$ is greater or less than $$1.$$
(2) Not sufficient. We know nothing about $$m.$$

(1) and (2): Now we know for sure that both $$m$$ and $$p-1$$ are positive.
Sufficient.

Since p<1 then p-1 is negative.
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Re: Is mp greater than m? [#permalink]  10 Oct 2012, 10:45
GetThisDone wrote:
Is mp greater than m?

(1) m > p > 0
(2) p is less than 1

Hello experts,

Could anyone please explain how to approach this problem algebraically. As detailed an explanation as possible will be greatly appreciated. I was trying to understand the following.

a. I am clear on getting the first set of roots based on the information given in the stem. i.e mp-m>o --> m(p-1)>0. So m>0 and P>1. But didn't understand the reasoning behind obtaining the second set of roots by flipping the signs.
b. Also need help on understanding how to use the obtained roots in conjunction with options (1) and (2).

m(p-1)>0. So m>0 and P>1. NO. It simply means that both $$m$$ and $$p-1$$ have the same sign, meaning either both are positive or both are negative.
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Kudos [?]: 624 [1] , given: 43

Re: Is mp greater than m? [#permalink]  10 Oct 2012, 10:51
1
KUDOS
Bunuel wrote:
EvaJager wrote:
GetThisDone wrote:
Is mp greater than m?

(1) m > p > 0
(2) p is less than 1

Hello experts,

Could anyone please explain how to approach this problem algebraically. As detailed an explanation as possible will be greatly appreciated. I was trying to understand the following.

a. I am clear on getting the first set of roots based on the information given in the stem. i.e mp-m>o --> m(p-1)>0. So m>0 and P>1. But didn't understand the reasoning behind obtaining the second set of roots by flipping the signs.
b. Also need help on understanding how to use the obtained roots in conjunction with options (1) and (2).

The question can be rephrased as "Is $$mp-m>0$$ or $$m(p-1)>0,$$ which is the same as asking whether $$m$$ and $$p-1$$ have the same sign?"

(1) Not sufficient. In order to know the sign of $$p-1$$ we have to know whether $$p$$ is greater or less than $$1.$$
(2) Not sufficient. We know nothing about $$m.$$

(1) and (2): Now we know for sure that both $$m$$ and $$p-1$$ are positive.
Sufficient.

Since p<1 then p-1 is negative.

Oooops! You are right. So, m is positive, p - 1 is negative, the answer to the stem question is a definite NO. Luckily, the answer is the same C.
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Re: Is mp greater than m? [#permalink]  10 Oct 2012, 23:25
Expert's post
GetThisDone wrote:
Is mp greater than m?

(1) m > p > 0
(2) p is less than 1

Hello experts,

Could anyone please explain how to approach this problem algebraically. As detailed an explanation as possible will be greatly appreciated. I was trying to understand the following.

a. I am clear on getting the first set of roots based on the information given in the stem. i.e mp-m>o --> m(p-1)>0. So m>0 and P>1. But didn't understand the reasoning behind obtaining the second set of roots by flipping the signs.
b. Also need help on understanding how to use the obtained roots in conjunction with options (1) and (2).

There are some great takeaways on number properties in this question. Let's look at them:

Question: Is mp greater than m?
Forget greater, think less because it is less intuitive so there will be fewer cases to worry about. When will the product of 2 numbers be less than one of them? Two simple cases we can think of are 6*(1/2) = 3 or 6*(-3) = -18 (One number is greater than 1 and the other is less than 1, one number is positive and the other is negative).
Numbers between 0 to 1 when multiplied to positive numbers, make the product smaller.
Numbers between 0 to 1 when multiplied to negative numbers, make the product greater because the product becomes 'less negative'.
Negative numbers when multiplied to positive numbers make the product smaller (negative).

Now go on to the statements:

(1) m > p > 0
This only tells us that both the numbers are positive. We don't know whether p is less than 1 or greater than 1. Not sufficient.

(2) p is less than 1
If p is less than 1, it will make the product mp less than m if m is positive. But if m is negative, the product will become greater. Not sufficient.

Using both, given that m is positive and p is less than 1, we can say that the product mp will be less than m. Hence, together both the statements are sufficient.

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Is mp greater than m? [#permalink]  23 May 2013, 00:44
u2lover wrote:
Is mp greater than m?

(1) m > p > 0

(2) p is less than 1

How can I practice a gazillion questions like this? I keep getting them wrong.
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Joined: 09 Sep 2013
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Kudos [?]: 61 [0], given: 0

Re: Is mp greater than m? [#permalink]  15 Jul 2014, 23:06
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Re: Is mp greater than m? [#permalink]  31 Jul 2014, 13:22
serendipiteez wrote:
u2lover wrote:
Is mp greater than m?

(1) m > p > 0

(2) p is less than 1

How can I practice a gazillion questions like this? I keep getting them wrong.

practice more I think. Here are some other examples

is-the-value-of-expression-k-m-1-greater-than-the-141322.html?fl=similar
if-m-is-a-positive-integer-greater-than-1-can-m-be-expressed-129063.html?fl=similar
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Re: Is mp greater than m?   [#permalink] 31 Jul 2014, 13:22
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