Finding the Fourth Proportional to 1,142.30, 1,576.40 and 644.91

Step by Step Solution

1. Step 1: Write the proportion equation
   1,142.30 : 1,576.40 = 644.91 : x
2. Step 2: Convert to fraction form
   1,142.30/1,576.40 = 644.91/x
3. Step 3: Cross multiply
   1,142.30x = 1,576.40 × 644.91
4. Step 4: Simplify right side
   1,142.30x = 1,016,625.02
5. Step 5: Solve for x
   x = 1,016,625.02/1,142.30
6. Step 6: Final answer
   x = 889.98