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Is 0.4 < x < 0.8 ?

Expert replies
Source: — Data Sufficiency |

Re: Is 0.4 < x < 0.8 ?

by Brent@GMATPrepNow » Sun Jun 14, 2020 11:47 am
BTGModeratorVI wrote:
Sat Jun 13, 2020 5:31 am
Is 0.4 < x < 0.8 ?

(1) 407x < 376
(2) 1400x > 1240

Answer: B
Source: Veritas Prep
Target question: Is 0.4 < x < 0.8?

Statement 1: 407x < 376
Divide both sides of the inequality by 407 to get: x < 376/407
Convert to a decimal to get: x < 0.92
There are several values of x that satisfy statement 1. Here are two:
Case a: x = 0.6. In this case, the answer to the target question is YES, x IS between 0.4 and 0.8
Case b: x = 0.1. In this case, the answer to the target question is NO, x is NOT between 0.4 and 0.8
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: 1400x > 1240
Divide both sides of the inequality by 1400 to get: x > 1240/1400
Simplify to get: x > 124/140
Simplify more: x > 31/35
Convert to decimal: x > 0.88
If x > 0.88, there are NO VALUES of x such that 0.4 < x < 0.8
In other words, the answer to the target question is NO, x is definitely NOT between 0.4 and 0.8
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: B

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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