-1/3 + -1/6 = ?

a) 1/3

b) -1/2

Question

-1/3 + -1/6 = ?

a) 1/3

b) -1/2

e.mccormick · Answer

Get a common denominator and then add them.

anonymous · Answer

so the common denominator is 18 right? @e.mccormick

e.mccormick · Answer

Well, that is a common denominator... but because $3\times 2 = 6$ I would just use 6. $\large \ddot \smile$

anonymous · Answer

@e.mccormick ok now.

e.mccormick · Answer

If you use 6, yout don't have to do anything to $-\dfrac{1}{6}$

e.mccormick · Answer

So, what do you do to $-\dfrac{1}{3}$?

anonymous · Answer

@e.mccormick ..

e.mccormick · Answer

Yes?  I am still here.  What do you need to change $-\dfrac{1}{3}$ into so it is over 6?

anonymous · Answer

I dont know.. @e.mccormick

anonymous · Answer

@e.mccormick I got the answer 1/3

anonymous · Answer

I mean -1/2

e.mccormick · Answer

Well, let me show you something:

$\dfrac{5}{7}\times \dfrac{4}{4}=\dfrac{20}{28}$

Yes, $-\dfrac{1}{2}$ was it.

Let me type that actual problem out in steps using 6 and you might see it.

e.mccormick · Answer

$-\dfrac{1}{3}+-\dfrac{1}{6}$

 $-\dfrac{1}{3}\times \dfrac{2}{2}+-\dfrac{1}{6}$

 $-\dfrac{2}{6}+-\dfrac{1}{6}$

 $-\dfrac{3}{6}$

 $-\dfrac{1}{2}$

e.mccormick · Answer

See how I just used the fact that 2x3=6 to decide what to do?  Because I knew I wanted to make the bottom of the fist fraction into 6, I knew that I had to multiply by a form of 1 that had a 2 in it.  Well, $\tfrac{2}{2}=1$, so I can multily by $\tfrac{2}{2}$ and it does not change the value of the fraction, it just changes what numbers are used.  Once I had 6 on the bottom of both, I added, simplified, and was done.