Step 1: Find the efficiency ratio of men to women

Since 48 men working for 5 days can do the same work as 40 women working for 9 days, we can equate the total work: $48 \times 5 \times M = 40 \times 9 \times W$

$240M = 360W \implies \frac{M}{W} = \frac{3}{2}$

Step 2: Calculate Total Work in terms of Men

Using the men's work capacity, Total Work = $48 \text{ men} \times 5 \text{ days} = 240 \text{ man-days}$.

$\text{Total Work} = 240 \text{ units}$

Step 3: Calculate the efficiency of the combined group

We need 4 men and 6 women. Since $M = 3$ and $W = 2$, substitute these values to find their combined one-day work:

$4M + 6W = 4(3) + 6(2) = 12 + 12 = 24 \text{ units/day}$

Step 4: Find the total number of days required

Divide the total work by the combined daily work of 4 men and 6 women:

$\text{Days} = \frac{240}{24} = 10 \text{ days}$