Finding the Fourth Proportional to 1,405.40, 1,938.65 and 815.85

Step by Step Solution

1. Step 1: Write the proportion equation
   1,405.40 : 1,938.65 = 815.85 : x
2. Step 2: Convert to fraction form
   1,405.40/1,938.65 = 815.85/x
3. Step 3: Cross multiply
   1,405.40x = 1,938.65 × 815.85
4. Step 4: Simplify right side
   1,405.40x = 1,581,643.52
5. Step 5: Solve for x
   x = 1,581,643.52/1,405.40
6. Step 6: Final answer
   x = 1,125.41