There is available 50 liters of a 40% solution of acid and water. What volume of water must be added to reduce the concentration to 10% ?

Question

amistre64 · Answer

a     + 50        = t         <-- quantities
a(1) + 50(.40) = t(.10)  <-- concentrations

anonymous · Answer

150 liters?

amistre64 · Answer

that and water has 0% acidity not 100%  :)

amistre64 · Answer

a     + 50        = t       ;*(-.10)
a(0) + 50(.40) = t(.10) 


a(-.10)+ 50(-.10)= t(-.10)
a   (0)  + 50(.40)  = t(.10) 
-----------------------
a(0-.10) +50(.4-.1) = 0

a(-.1) +50(.3) = 0

a(-.1) +15 = 0

a = 15/.1 = 150

anonymous · Answer

Again, I just solved $$ x-0.9x = 15 $$

amistre64 · Answer

pffft!!  thats how they do it in kindergarten.  At my age we do "real" math ;)

anonymous · Answer

between two what si the correct answer ?..

amistre64 · Answer

our answers seem to converge on 150; but i havnt taken the limit of that yet

anonymous · Answer

lol @amistre64

anonymous · Answer

ok tnx ... :-)

anonymous · Answer

Glad to help :)

anonymous · Answer

40% * 50 + water = 10% ( 50 + L )
-> L = 200 - 50 = 150 L of water