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If 0 < r < 1 < s < 2, which of the following mus

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by AAPL » Sun Jan 28, 2018 2:00 pm
If 0 < r < 1 < s < 2, which of the following must be less than 1?

I. r/s
II. rs
III. s - r

A. I only
B. II only
C. III only
D. I and II
E. I and III

The OA is A.

I don't have clear this PS question. Can any expert give an example of why II does not work? I just can't figure it out.I appreciate if any expert explain it for me. Thank you so much.
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Source: — Problem Solving |

by Brent@GMATPrepNow » Sun Jan 28, 2018 2:43 pm
AAPL wrote:If 0 < r < 1 < s < 2, which of the following must be less than 1?

I. r/s
II. rs
III. s - r

A. I only
B. II only
C. III only
D. I and II
E. I and III
I) r/s
r and s are both POSITIVE, and r is less than s.
So, it MUST be the case that r/s < 1


II) rs
It could be the case that r = 0.9 and s = 1.8, in which case rs = 1.62
So, it NEED NOT be the case that rs < 1

III) s - r
It could be the case that r = 0.1 and s = 1.8, in which case s - r = 1.7
So, it NEED NOT be the case that s - r < 1

Answer: A

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by Scott@TargetTestPrep » Wed Jan 31, 2018 4:26 pm
AAPL wrote:If 0 < r < 1 < s < 2, which of the following must be less than 1?

I. r/s
II. rs
III. s - r

A. I only
B. II only
C. III only
D. I and II
E. I and III
We are given that 0 < r < 1 < s < 2 and need to determine which Roman Numeral expressions must be less than 1. Let's test each expression.

I. r/s

Since r is less than s and both r and s are positive, r/s will always be less than 1. Roman numeral I is correct.

II. rs

The product of r and s does not have to be less than 1. For example, if r = 0.8 and s = 1.5 the product of r and s will be (0.8)(1.5) = 1.2, which is greater than 1. Roman numeral II is not correct.

III. s - r

s - r does not have to be less than 1. For example, if s = 1.9 and r = 0.1, s - r = 1.8. Roman number III is not correct.

Answer: A

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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