There are three testing tubes A, B and C each with 10, 20 and 30 grams of pure water. You pour 10 grams of salt water with x% concentration into Tube A, fully mix it, take out 10 grams of the mixture and pour it into Tube B. After fully mixing Tube B, take out 10 grams of mixture from Tube B and pour it into Tube C. The final salt concentration in Tube C is 0.5%. What’s the salt concentration of the solution that you first poured into Tube A?
+128475 The amount of the first salt concentration = x /10 where x is in grams
Final salt concentration (per gram) in Tube A after mixing = x / (10 + 10) = x /20
So....the amt poured into B * concentration per gram = 10 grams * (x/20) = x/2 grams
So....the final concentration in B is (x/2) / (10 +20) = = x/60
And the amout poured into C * concentration = 10 ( x/60) = x/6 grams
So....the final concentration in C is ( x/6) / (10 + 30) = x/ 240
x/240 = .005
x = 240 * .005 = 1.2
So....the first salt concentration = 1.2 / 10 = 12%
