A mixture of 150 litres of wine and water contains 20% water (and the rest is wine). Additional water is added to this mixture.\nHow many litres of water must be added so that in the new mixture, water becomes 25% of the total mixture volume?

Introduction:
This question is about changing concentration by adding one component (water). The amount of wine stays constant, while total volume increases. We use the percentage definition: water% = (water amount / total mixture) * 100, and solve for the added water.

Given Data / Assumptions:

• Total mixture initially = 150 litres
• Initial water percentage = 20%
• Initial water amount = 20% of 150
• Target water percentage = 25%
• Only water is added

Concept / Approach:
Compute initial water amount. Let x litres water be added. Then:\n(initial water + x) / (150 + x) = 0.25.

Step-by-Step Solution:
Initial water = 20% of 150 = (20/100) * 150 = 30 litresLet added water = x litresNew water amount = 30 + xNew total mixture = 150 + xTarget condition: (30 + x) / (150 + x) = 0.2530 + x = 0.25(150 + x) = 37.5 + 0.25xx - 0.25x = 37.5 - 300.75x = 7.5x = 10 litres

Verification / Alternative Check:
After adding 10 litres:\nWater = 30 + 10 = 40 litres.\nTotal = 150 + 10 = 160 litres.\nWater% = 40/160 = 0.25 = 25%, correct.

Why Other Options Are Wrong:
5 litres: gives water% less than 25%.15, 20, 25 litres: makes water% greater than 25%.

Common Pitfalls:
Adding 5% of 150 directly (but total changes after adding).Assuming wine amount changes; only water changes here.Using 25% of 150 instead of 25% of (150 + x).

Final Answer:
10 litres