If an alloy contains copper and silver in the ratio 3:7, then the percentage quantity of silver in the alloy is: 

  (A) 90%  

   (B) 70%

   (C) 60%  

   (D) None of these

Answer:

(b) 70%

Step-by-step explanation:

let the total quantity be 10x.

copper will be 3x and silver will be 7x.

Now, silver %= (quantity of silver/total quantity) × 100

= (7x/10x) × 100

=70%