In a mixture of 25 litres, the ratio of milk to water is 4:1. If another 3 litres of water is added to the mixture (without removing anything), what will be the new ratio of milk to water?

Introduction / Context:
This is a straightforward mixture ratio update problem. The mixture initially has milk and water in a known ratio. When you add water only, the milk quantity remains the same and only the water quantity changes. To avoid confusion, convert the ratio into actual litres using the total volume, then add the extra water, and finally simplify the new ratio. This method is reliable for all “add water” ratio questions.

Given Data / Assumptions:

• Total mixture = 25 litres
• Initial milk:water = 4:1
• Added water = 3 litres
• Nothing is removed

Concept / Approach:
Total parts = 4 + 1 = 5. Milk = (4/5)*25 and water = (1/5)*25. After adding 3 litres of water, water becomes (5 + 3). Then form the ratio milk:water and simplify.

Step-by-Step Solution:
Total parts = 5 Milk = (4/5) * 25 = 20 litres Water = (1/5) * 25 = 5 litres New water = 5 + 3 = 8 litres New ratio = 20 : 8 Simplify by 4 => 5 : 2

Verification / Alternative check:
The ratio must become smaller than 4:1 because water increased. 5:2 is 2.5:1, which is smaller than 4:1, so the direction of change is consistent with the operation performed.

Why Other Options Are Wrong:
5:1 implies too little water (would correspond to 20:4, not 20:8). 5:3 and 5:4 do not match 20:8 after simplification. 4:3 is not equal to 20:8 and often appears from swapping numbers incorrectly.

Common Pitfalls:
Adding 3 to total and forgetting it is specifically added to water, not simplifying 20:8 properly, or using ratio parts without converting to litres correctly.

Final Answer:
The new ratio of milk to water is 5:2.