Finding the Fourth Proportional to 1,091.31, 1,636.05 and 432.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,091.31 : 1,636.05 = 432.78 : x
2. Step 2: Convert to fraction form
   1,091.31/1,636.05 = 432.78/x
3. Step 3: Cross multiply
   1,091.31x = 1,636.05 × 432.78
4. Step 4: Simplify right side
   1,091.31x = 708,044.78
5. Step 5: Solve for x
   x = 708,044.78/1,091.31
6. Step 6: Final answer
   x = 648.80