Çözüldü Solving Problems Using Proportionality and One-Variable Equations

If 12 liters of water are needed to fill a jerrycan after 4/7 of the water in the jerrycan is used and two-thirds of the remaining water is used up, what is the total capacity of the jerrycan?

A) 84
B) 63
C) 56
D) 35
E) 14

Solution - 1:
The capacity of the jerry can: x pieces
6 pieces =======> 12 liters
1 piece ========> 2 liters
x = 7 pieces = 7·2 = 14 liters.

Solution - 2:
The capacity of the jerry can: x liters
x - [ (x - 4x / 7) - (x - 4x / 7)·(2 / 3) ] = 12 ⇒ x = 14 liters.

Check By WolframAlpha: https://www.wolframalpha.com/input?i=x - [ (x - 4x / 7) - (x - 4x / 7)(2/3) ] = 12

Note: Solving the equation is homework for the interested students.

Kaynak: FDD Dershaneleri, Final "Matematik - 1, Konu Anlatımlı", Sayfa 106, Örnek 4