Problem:
A ladder has rungs 25 cm apart. The rungs decrease uniformly in length from 45 cm at the bottom to 25 cm at the top. If the top and bottom rungs are 2.5 m apart, what is the length of the wood required for the rungs?

Solution:

To calculate the length of the wood required for the rungs, we need to find the total length of all the rungs combined. We can break down the problem into smaller steps to find the solution.

Step 1: Calculate the number of rungs on the ladder
- The distance between the top and bottom rungs is given as 2.5 m.
- Since the rungs are 25 cm apart, we need to convert the distance to centimeters.
- 2.5 m = 250 cm
- The number of rungs can be found by dividing the total distance by the distance between each rung.
- Number of rungs = 250 cm / 25 cm = 10

Step 2: Calculate the difference in length between each pair of consecutive rungs
- The length of the rungs decreases uniformly from 45 cm at the bottom to 25 cm at the top.
- The difference in length between each pair of consecutive rungs can be found by subtracting the length of the rung above from the length of the rung below.
- Difference in length = 45 cm - 25 cm = 20 cm

Step 3: Calculate the length of the wood required for each rung
- The length of the wood required for each rung is the average of the lengths of the rungs it connects.
- Length of the wood required for each rung = (Length of rung above + Length of rung below) / 2
- Length of the wood required for each rung = (45 cm + 25 cm) / 2 = 35 cm

Step 4: Calculate the total length of the wood required for all the rungs
- The total length of the wood required for all the rungs can be found by multiplying the length of each rung by the number of rungs.
- Total length of the wood required = Length of wood required for each rung * Number of rungs
- Total length of the wood required = 35 cm * 10 = 350 cm

Conclusion:
The length of the wood required for the rungs is 350 cm.