Which number below is the same as ( -2/3) - (-(-3/5))?a. 4/15   b.-4/15  c. -1/2   d. -19/15

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hala718's profile pic

hala718 | High School Teacher | (Level 1) Educator Emeritus

Posted on

-2/3 - (- ( -3/5)

Let us re-write:

-2/3 -1(-1)-3/5)

First we will start from the right to the left.

We know that -1*-3/5 = + 3/5

==> -2/3 - (-(-3/5) = -2/3 -1 ( + 3/5)

Also, -1*+3/5 = -3/5

==> -2/3 -(-(-3/5) = -2/3 - 3/5

 Now we will re-write using the common denominator ( 15).

==> -2/3- 3/5 = ( -2*5 - 3*3) / 15

                        = -10 - 9 ) / 15

                         = -19 / 15

Then the answer is (d).

-2/3 - (-(-3/5) = -19/15

neela's profile pic

neela | High School Teacher | (Level 3) Valedictorian

Posted on

To simplify and choose the number:

 ( -2/3) - (-(-3/5)).

 ( -2/3) - (-(-3/5)) =  ( -2/3) - {-(-3/5))}.

 ( -2/3) - (-(-3/5)) =  ( -2/3) - (3/5),  as  -(-x) = +x or x.

 ( -2/3) - (-(-3/5)) = (-2/3) - 3/5 =  -(2/3+3/5) .

( -2/3) - (-(-3/5) = - {2*5/3*5 +3*3/5*3), as LCM  of denominators = 3*5 = 15.

( -2/3) - (-(-3/5) = -(10+9)/15 = -19/15.

So choice d is correct.

 

 

 

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