Finding the Fourth Proportional to 1,139.12, 1,572.00 and 641.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.12 : 1,572.00 = 641.72 : x
2. Step 2: Convert to fraction form
   1,139.12/1,572.00 = 641.72/x
3. Step 3: Cross multiply
   1,139.12x = 1,572.00 × 641.72
4. Step 4: Simplify right side
   1,139.12x = 1,008,772.77
5. Step 5: Solve for x
   x = 1,008,772.77/1,139.12
6. Step 6: Final answer
   x = 885.57