Finding the Fourth Proportional to 1,018.38, 1,405.17 and 645.42

Step by Step Solution

1. Step 1: Write the proportion equation
   1,018.38 : 1,405.17 = 645.42 : x
2. Step 2: Convert to fraction form
   1,018.38/1,405.17 = 645.42/x
3. Step 3: Cross multiply
   1,018.38x = 1,405.17 × 645.42
4. Step 4: Simplify right side
   1,018.38x = 906,924.82
5. Step 5: Solve for x
   x = 906,924.82/1,018.38
6. Step 6: Final answer
   x = 890.56