How do I know if two fractions are proportions?

Question

Use division to determine whether the ratios form a proportion.

5/7 and 30/42

 

 Please help.

Answer 1

Cross Multiplication should give the same result.

 

     1/2 = 25/50

 

       50 *1 = 2 * 25

 

       To simplify each fraction , divide both numerator and denominator by their GCF( greatest common factor), should make all fractions equal to their face value

 

 i,e.      1/2 = 25/ 50

                 

                  = 25/25  / 50/25        / 25 is GCF of 25& 50

 

                   =  1 / 2

Answer 2

Divide numerator of the second fraction by numerator of the first one. Repeat the same for denominators. If the ratio remains the same then your fractions are proportions.

 

Check it now. 30/5 = 42/7 = 6 - yes, they are proportions.