Finding the Fourth Proportional to 1,815.31, 2,505.90 and 1,218.70

Step by Step Solution

1. Step 1: Write the proportion equation
   1,815.31 : 2,505.90 = 1,218.70 : x
2. Step 2: Convert to fraction form
   1,815.31/2,505.90 = 1,218.70/x
3. Step 3: Cross multiply
   1,815.31x = 2,505.90 × 1,218.70
4. Step 4: Simplify right side
   1,815.31x = 3,053,940.33
5. Step 5: Solve for x
   x = 3,053,940.33/1,815.31
6. Step 6: Final answer
   x = 1,682.32