A 50 litre mixture of water and alcohol contains 10% alcohol. How much more alcohol must be added to make the strength of alcohol 40% in the new mixture?
(a)25
(b)30
(c)20
(d)23

Options

A. 25
B. 30
C. 20
D. 23

Explanation

To solve the problem, we need to determine how much more alcohol must be added to a 50-litre mixture that currently contains 10% alcohol in order to increase the alcohol concentration to 40%.

### Step-by-step Solution:

1. **Calculate the initial amount of alcohol in the mixture:**
The mixture is 50 litres and contains 10% alcohol.
\[
\text{Initial alcohol} = 10\% \text{ of } 50 \text{ litres} = \frac{10}{100} \times 50 = 5 \text{ litres}
...