Multiple choice

How many litres of mixture from an 80 litre drum, full of 80% concentrated milk, have to be replaced with water to make the resultant mixture 60% concentrated?

  1. 10

  2. 15

  3. 20

  4. 30

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let x be the amount replaced. Final concentration = (Initial amount * Initial conc - x * Initial conc) / Total volume = (80 * 0.8 - x * 0.8) / 80 = 0.6. 64 - 0.8x = 48. 0.8x = 16. x = 20.

AI explanation

Using the replacement formula, Final Concentration equals Initial Concentration multiplied by (1 minus replaced quantity divided by total volume) raised to the number of replacements. Plugging in the values gives 60% equals 80% multiplied by (1 minus x divided by 80). Solving (1 minus x divided by 80) equals 0.75 yields x divided by 80 as 0.25, so the replaced quantity is 20 litres.

Keep practicing — related questions