Finding the Fourth Proportional to 1,018.86, 1,406.34 and 645.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,018.86 : 1,406.34 = 645.72 : x
2. Step 2: Convert to fraction form
   1,018.86/1,406.34 = 645.72/x
3. Step 3: Cross multiply
   1,018.86x = 1,406.34 × 645.72
4. Step 4: Simplify right side
   1,018.86x = 908,101.86
5. Step 5: Solve for x
   x = 908,101.86/1,018.86
6. Step 6: Final answer
   x = 891.29