Number line need help

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sanjib.saha: Senior | Next Rank: 100 Posts; Posts: 30; Joined: Sun Jul 26, 2009 9:58 am; Location: Kolkata

Number line need help

by sanjib.saha » Tue Aug 28, 2012 8:59 pm

Hello, we all know that 1 < 2. If we multiply each side by -1 then the sign flips. So -1 > -2, which is correct. Now 1/2 < 1 then if we multiple each side by -1 then the sign flips. So we get -1/2 > -1, which is incorrect. So am I misunderstanding the multiply by -1 concept?

Sanjib

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Source: Beat The GMAT — Problem Solving | Tue Aug 28, 2012 8:59 pm

alex.gellatly: Master | Next Rank: 500 Posts; Posts: 435; Joined: Wed Nov 16, 2011 7:27 am; Thanked: 48 times; Followed by:16 members

by alex.gellatly » Tue Aug 28, 2012 9:11 pm

sanjib.saha wrote:Hello, we all know that 1 < 2. If we multiply each side by -1 then the sign flips. So -1 > -2, which is correct. Now 1/2 < 1 then if we multiple each side by -1 then the sign flips. So we get -1/2 > -1, which is incorrect. So am I misunderstanding the multiply by -1 concept?

You are not misunderstanding the multiply (or divide) by a negative number you flip the sign. What are you missunderstand, however, is that -1/2 is > -1 For a visual representation look at the line:

______-2___A__-1___B__0_____1______2_____ <-- Where would -1/2 be at A or B? at B or course! That means that -1/2 > -1.

Let me know if this helps

A useful website I found that has every quant OG video explanation:

https://www.beatthegmat.com/useful-websi ... tml#475231