Question

in what proportion should a solution of 95%,80%,60% and 50% acid be mixed to produce a solution of 70% acid

Answer 1

95 mL of 95 % acidic solution is taken along with 100 mL  solution of each  80 % acidic solution in additionn to 60 % solution and 50 % solution

The overall concentration can be determined as:

$Overall concentration =  (M _1 V_1 + M_2 V_2 + M_3 V_3 + M_4 V_4) / 4$

Where, M is molarity of acidic solution and V is volume added

$(95/100 * 95 + 80/100 * 100 + 60 /100 * 100 + 50 /100 * 100 )/4$

$(90.25 + 80 + 60 + 50) /4$

$70.0625 %$

Thus, by including 95 % of 95 % acidic solution along with to 100 % each solution of 80 % acidic solution with 60% acidic solution with 50% acidic solution, an overall concentration of 70 % acidic solution can be obtained.