Finding the Fourth Proportional to 1,404.90, 1,938.78 and 815.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,404.90 : 1,938.78 = 815.40 : x
2. Step 2: Convert to fraction form
   1,404.90/1,938.78 = 815.40/x
3. Step 3: Cross multiply
   1,404.90x = 1,938.78 × 815.40
4. Step 4: Simplify right side
   1,404.90x = 1,580,881.21
5. Step 5: Solve for x
   x = 1,580,881.21/1,404.90
6. Step 6: Final answer
   x = 1,125.26