Finding the Fourth Proportional to 1,018.33, 1,405.19 and 645.30

Step by Step Solution

1. Step 1: Write the proportion equation
   1,018.33 : 1,405.19 = 645.30 : x
2. Step 2: Convert to fraction form
   1,018.33/1,405.19 = 645.30/x
3. Step 3: Cross multiply
   1,018.33x = 1,405.19 × 645.30
4. Step 4: Simplify right side
   1,018.33x = 906,770.72
5. Step 5: Solve for x
   x = 906,770.72/1,018.33
6. Step 6: Final answer
   x = 890.45