A and B are two alloys of gold and copper prepared by mixing metals in the ratio 7 :2 and 7 : 11 respectively. If equal quantities of the alloys are melted to form a third alloy C, the ratio of gold and copper in C will be

ratio of gold and copper in A = 7 : 2

gold in A = $$ \frac{7}{9} $$

copper in A = $$ \frac{2}{9} $$

ratio of gold and copper in B = 7 : 11

gold in B = $$ \frac{7}{18} $$

copper in B = $$ \frac{11}{18} $$

If equal quantities of the alloys are melted to form a third alloy C

gold in C = $$ \frac{7}{9} + \frac{7}{18} = \frac{21}{18} $$

copper in C = $$ \frac{2}{9} + \frac{11}{18} =\frac{15}{18} $$

ratio of gold and copper in C = 21 : 15 = 7 : 5