Let the amount of work completed by B in 1 day be $B$ units. Then, the amount of work completed by A in 1 day is $4B$ units (since A is 4 times faster than B).

Together, A and B complete the work in 5 days. Therefore, their combined work rate is:

$\text{Work rate of A + Work rate of B} = \frac{1}{5} \, \text{(since they complete the work in 5 days)}.$

This means:

$4B + B = \frac{1}{5}.$

Simplifying:

$5B = \frac{1}{5}.$

Solving for $B$:

$B = \frac{1}{25}.$

Thus, B completes $\frac{1}{25}$ of the work in 1 day, which means B will take 25 days to complete the work alone.

Answer: B can complete the work in 25 days.

Would you like a further breakdown of this solution or to ask related questions?

Here are some related questions:

1. What if A were 3 times as efficient as B instead of 4?
2. How would the solution change if they completed the work together in 6 days?
3. How do we interpret work rates in more complex real-world problems?
4. How can we set up a similar problem where A is slower than B?
5. What if A and B had different work rates that are not multiples of each other?

Tip: Always ensure units (like days or work completed per day) are consistent throughout the problem.