A dishonest shopkeeper sells milk at 20% gain and also, he adds water in the ratio 4:1 in it. What is his total profit?

Hint: In the given question consider the amount of one litre is Rs.100. Then convert the milk to water ratio (4:1) to gain a percentage ratio to find the total profit percentage easily. So, use this concept to reach the solution of the question.

Complete step-by-step answer:
In the case of milk & water. The milk amount is considered as Rs.100.
Now during the comparison of water with milk, the water amount is taken as profit percentage
Here \[{\text{milk : water }} = 4:1\]
Multiplying the ratio with 25, we have
\[{\text{milk : water }} = 100:25\]
So, the dishonest shopkeeper makes 25% profit on adding water to the milk.
But he gains 20% by selling the milk.
Therefore, total profit percentage \[ = 25 + 20 + \dfrac{{25 \times 20}}{{100}} = 25 + 20 + 5 = 50\% \]
Thus, the total profit percentage is 50%.

Note: In these types of problems, sometimes they ask for the value from this problem. The value of the problem is “Honesty is the best policy” and never cheat customers for more profits.