Finding the Fourth Proportional to 1,290.31, 1,780.47 and 730.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,290.31 : 1,780.47 = 730.78 : x
2. Step 2: Convert to fraction form
   1,290.31/1,780.47 = 730.78/x
3. Step 3: Cross multiply
   1,290.31x = 1,780.47 × 730.78
4. Step 4: Simplify right side
   1,290.31x = 1,301,127.42
5. Step 5: Solve for x
   x = 1,301,127.42/1,290.31
6. Step 6: Final answer
   x = 1,008.39