Finding the Fourth Proportional to 1,142.68, 1,576.89 and 645.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,142.68 : 1,576.89 = 645.31 : x
2. Step 2: Convert to fraction form
   1,142.68/1,576.89 = 645.31/x
3. Step 3: Cross multiply
   1,142.68x = 1,576.89 × 645.31
4. Step 4: Simplify right side
   1,142.68x = 1,017,582.89
5. Step 5: Solve for x
   x = 1,017,582.89/1,142.68
6. Step 6: Final answer
   x = 890.52