Finding the Fourth Proportional to 1,038.72, 1,433.52 and 645.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,038.72 : 1,433.52 = 645.72 : x
2. Step 2: Convert to fraction form
   1,038.72/1,433.52 = 645.72/x
3. Step 3: Cross multiply
   1,038.72x = 1,433.52 × 645.72
4. Step 4: Simplify right side
   1,038.72x = 925,652.53
5. Step 5: Solve for x
   x = 925,652.53/1,038.72
6. Step 6: Final answer
   x = 891.15