DisciplinedPrep wrote:
729 liters of a mixture contains milk and water in the ratio 7:2. How much water must be added to get a new mixture containing milk and water in the ratio 7:3?
A. 100 liters
B. 81 liters
C. 72.9 liters
D. 90 liters
E. 50 liters
#Work-Backwards Strategy
If Milk:Water is 7:2 in 729 Liters, then milk is 567 Liters.
Final mixture is 729+x liters (x liters of water added)
Option D (x=90)
Final amount of milk: (729+90)*7/10 does not equal 567 Liters of Milk.
Skip Option D.
Option B (x=81)
Final amount of milk: (729+81)*7/10 equals 567 Liters of Milk.
Option B is the right Answer.