How many liters of a 90% of concentrated acid needs to be mixed with a 75% solution of concentrated acid to get a 30 liter solution of 78% concentrated acid?
a) 8 b)9 c) 7 d)6

• the concentration is given which is wrt 100, hence we can take x lt of 90% and (30-x)of 75%
  
  x*90 + (30-x)*75 = 30*78 hence the ans is 6 ltr...
• 11 years agoHelpfull: Yes(124) No(4)
• ratio of mixing90% conc acid with solution of 75%acid is 1:4
  and overall mixture is of 30 liter
  so only one ratio of answer 6:24 satisfies it
  
  so.........ans is 6
• 11 years agoHelpfull: Yes(16) No(27)
• form indiabix Mixture or alligation
  
  http://www.indiabix.com/aptitude/alligation-or-mixture/formulas
  
  C.p = 90
  d=75
  m=78
  m-d=3
  c.p-m= 12
  now final proportion required is in ratio of m-d / c.p-m
  which is 1:4
  total amount is 30 liter
  
  amount of 90% concentrated acid to be added [ m-d ] is (1 / (1+4) )* 30
  
  ans is 6L
• 8 years agoHelpfull: Yes(11) No(4)
• d) 6
  ratio=90-78:78-75
  =12:3
  12x+3x=30lit.
  x=2.
  thus 3*2=6 lit of 90% concentrated acid
• 8 years agoHelpfull: Yes(10) No(1)
• 78= 90*n1+75*n2/n1+n2
  78n1+78n2=90n1+75n2
  n1/n2=3/12=1/4
  n1:n2=1:4
  x+4x=30, x=6lit ans
• 8 years agoHelpfull: Yes(7) No(0)
• ratio of mixing 90% concentrated acid with solution of 75%acid is 1:4
  to get 30 liter solution of 78% concentrated acid
  (1/5)*30=6
  ans is 6 liter
• 9 years agoHelpfull: Yes(4) No(4)
• 90% 78%
  75%
  3% 15%
  
  1:5lit so (we need 30 get 6L)
• 8 years agoHelpfull: Yes(2) No(3)
• 90 75
  78
  (78-75)3 12(90-78)
  1:4
  1+4=5parts
  given is 30 lit so 30/5=6
• 6 years agoHelpfull: Yes(1) No(1)
• c.p of concentrated acid :90
  c.p of solution of concentrated acid is:75
  mean price:78
  90-78=12
  78-75=3
  3:12=>1:4
  30*1/5=6.
• 4 years agoHelpfull: Yes(0) No(0)