In a mixture of 35 litres, the ratio of milk to water is 4:1. If 7 litres of water is added to this mixture (and nothing is removed), what will be the new ratio of milk to water in the resulting mixture?

Introduction / Context:
This question checks the core idea of mixture ratios. When you add only water to a milk-water mixture, the amount of milk stays exactly the same, while the amount of water increases. The ratio changes because the denominator side (water) changes, but the numerator side (milk) does not. The safest way to solve is to convert the ratio into actual litres, perform the addition, and then simplify the new ratio.

Given Data / Assumptions:

• Total mixture = 35 litres
• Milk : Water = 4 : 1
• Water added = 7 litres
• No milk removed, no mixture removed

Concept / Approach:
If milk:water = 4:1, total parts = 5. Milk is 4/5 of the mixture and water is 1/5 of the mixture. After adding water, milk remains constant but water becomes (original water + added water). Finally, simplify the ratio.

Step-by-Step Solution:
Total parts = 4 + 1 = 5 Milk = (4/5) * 35 = 28 litres Water = (1/5) * 35 = 7 litres New water = 7 + 7 = 14 litres New ratio = 28 : 14 Simplify by 14 => 2 : 1

Verification / Alternative check:
Originally water was 7 litres. After adding 7 litres, water doubles to 14 litres, while milk stays 28 litres. So the ratio should become half of 4:1, which is 2:1. This quick logic matches the computed answer.

Why Other Options Are Wrong:
4:1 is the original ratio and ignores the added water. 5:4 and 4:5 come from mixing up milk and water or simplifying incorrectly. 1:2 reverses the dominance even though milk is still greater than water here.

Common Pitfalls:
Adding 7 litres to the total but forgetting it is added specifically to water, not recomputing milk and water from parts, or not simplifying 28:14 correctly.

Final Answer:
The new ratio of milk to water is 2:1.