Question 923108
total quantity of solution = 10 ml
quantity of Acid = 10 % of 10 ml
                  ={{{10/100*10}}}
                   = 1 ml
let as assume v ml of water is added to 10ml of a 10% acid solution to make it a 5% solution
      total quantity of solution now =  (10+v) ml
      quantity of acid  =  5% of (10+v) ml
                         = {{{5/100 *(10+v)}}}
                         ={{{1/20*(10+v)}}}
but , quantity of acid remains same even after adding water
so    1  =  {{{1/20*(10+v)}}}
     multiply with 20 on both sides
      1*20 = {{{1/20*(10+v)*20}}}
 20  =10+v
move 10 to the left
20-10 =v
10 =v
quantity of water added  = 10 ml