Algebra

 

Compute    
\frac{1}{1 \times 4} + \frac{1}{7 \times 10}    

 

1 / (1 • 4)  +  1 / (7 • 10)     

 

1 / 4  +  1 / 70    

 

You need a common denominator.    

It need not to be the lowest common denominator; you can reduce the answer later, if necessary.    

You can always get a common denominator by multiplying the two together.  This one can be 280.    

 

70 / 280  +  4 / 280  =  74 / 280  =  37 / 140     (Could have used 140 as the common denominator.)    

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