Finding the Fourth Proportional to 1,018.71, 1,405.65 and 645.03

Step by Step Solution

1. Step 1: Write the proportion equation
   1,018.71 : 1,405.65 = 645.03 : x
2. Step 2: Convert to fraction form
   1,018.71/1,405.65 = 645.03/x
3. Step 3: Cross multiply
   1,018.71x = 1,405.65 × 645.03
4. Step 4: Simplify right side
   1,018.71x = 906,686.42
5. Step 5: Solve for x
   x = 906,686.42/1,018.71
6. Step 6: Final answer
   x = 890.03