From Kaplan 800 - Please confirm answers

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From Kaplan 800 - Please confirm answers

by adi_800 » Mon Aug 15, 2011 11:15 pm
Two problems: I do not have OAs. So, please confirm answers.

1. x, y, z -> All positive integers.
0<x<y<z.
x: Even, y: Odd, Z: Prime.
What is the possible value of x+y+z?
Options: A. 4
B. 5
C. 11
D. 15
E. 18.

[spoiler]My Approach: Even + Odd + Odd (Since z is greater than 2) = Even. 4 is not possible. Hence Ans is E[/spoiler]

2. a and b are integers such that 1 + b = 5. Which of the following is true?
I. a*b is odd
II. If a is off, b is even
III. If a is negative, b is positive.

Options: A. I only
B. II only
C. I and II only
D. II and III only
E. I, II, and III

[spoiler]
My approach: since the sum is odd, either of them can be even or odd but not both. So, the product will be even. So, I is not true
If one is odd, then other is even. So, II must be true.
If one is negative, then other must be bigger and hence positive to make sure that the sum is positive. Hence the correct answer is D[/spoiler]
Source: — Problem Solving |

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by Anurag@Gurome » Mon Aug 15, 2011 11:30 pm
adi_800 wrote:1. x, y, z -> All positive integers.
0<x<y<z.
x: Even, y: Odd, Z: Prime.
What is the possible value of x+y+z?
As x is an even integer greater than 0, minimum value of x is 2.
As y is an odd integer greater than x, minimum value of y is 3.
As z is an prime integer greater than y, minimum value of z is 5 and z will be an odd integer too.

Hence, (x + y + z) = (Even + odd + odd) = Even

Thus, either option A or E is correct.
Now (x + y + z) cannot be equal to 4 as minimum value of (x + y + z) is (2 + 3 + 5) = 10

So option E is only possible solution.
The correct answer is E.
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by Anurag@Gurome » Mon Aug 15, 2011 11:47 pm
adi_800 wrote:2. a and b are integers such that 1 + b = 5. Which of the following is true?
I. a*b is odd
II. If a is off, b is even
III. If a is negative, b is positive.
I feel the correct question says (a + b) = 5

As the sum of a and b is odd, one of them is even and the other one is odd. Hence, their product must be even. Thus, I is not true but II is definitely true.

If a is negative, then b has to be positive to make their sum positive.

Hence,only II and III are true.

The correct answer is D.
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GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
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