Finding the Fourth Proportional to 1,139.16, 1,572.04 and 641.92

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.16 : 1,572.04 = 641.92 : x
2. Step 2: Convert to fraction form
   1,139.16/1,572.04 = 641.92/x
3. Step 3: Cross multiply
   1,139.16x = 1,572.04 × 641.92
4. Step 4: Simplify right side
   1,139.16x = 1,009,123.92
5. Step 5: Solve for x
   x = 1,009,123.92/1,139.16
6. Step 6: Final answer
   x = 885.85