how many liters of a 70% acid question must be mixed with a 20% acid solution to get 350 L of a 60% acid solution? plz help

Question

pphalke · Answer

first person to solve this will get a medal

welshfella · Answer

x = volume of 70% solution and y = volume of the 20%
so we can write

x + y = 350

welshfella · Answer

we can create another equation using amounts of pure acid 
0.7x  is the volume of pure acid in the 70% solution

0.70x + 0.20y = 0.60*350

0.7x + 0.20y = 210

pphalke · Answer

how do i solve this?

welshfella · Answer

to solve for x and y the first thing you do is multiply the second equation by -5:
x + y = 350 -------(1)

0.70x + 0.20y = 210       Multiply whole equation by -5


-3.5x - y  = -1050   --  (2)


ow add equations (1) and (2)  . This will eliminate y and you can find value of x

pphalke · Answer

how do i add those ?

08surya · Answer

(70%)x+(20%)(350-x)=350*60%

solve this

08surya · Answer

(70%)x+(20%)(350-x)=350*60%

70x+ 7000-20x=21000
50x=14000
5x=1400
x=280

pphalke · Answer

so @08surya ur saying that you need 280 liters to get 350 liters of a 60% acid solution

pphalke · Answer

sorry 70% acid solution

08surya · Answer

yup......m i wrong?

welshfella · Answer

280 L of 70% acid is correct