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Help #4

NotSoSmart  Feb 23, 2018
 #1
avatar+88898 
+2

The trick here, NSS....is just to simplify the numerator first and then the denominator......so we have

 

2/5t  - 3/3t  =

 

2/5t  -  1/t          multiply the second fraction by  5 on top/bottom

 

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

 

The denominator becomes

 

1/2t  +  1/2t  =   2/2t  =  1/ (t)

 

So  we have

 

(-3/5)t  ÷ 1/t        flip the second fraction and multiply

 

-3 / (5t)  *  (t)/ 1  =    -3t / 5t   =   -3/5

 

Do you see how to do this??

 

 

Second one :

 

1/ 20   =  1/r1  - 1/75       subtract  1/75  from  both sides

 

(1/20) - (1/75)  =  1/r1

 

The common denominator  on the left is 300

 

15/300  - 4/300  =  1/r1

 

(11/300)    =  1/r1

 

To find r1, just flip both fractions over

 

300/ 11  =  r1/1

 

300/11  =  r≈  27 ohms

 

 

cool cool cool

CPhill  Feb 23, 2018

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