Finding the Fourth Proportional to 1,142.05, 1,576.08 and 644.71

Step by Step Solution

1. Step 1: Write the proportion equation
   1,142.05 : 1,576.08 = 644.71 : x
2. Step 2: Convert to fraction form
   1,142.05/1,576.08 = 644.71/x
3. Step 3: Cross multiply
   1,142.05x = 1,576.08 × 644.71
4. Step 4: Simplify right side
   1,142.05x = 1,016,114.54
5. Step 5: Solve for x
   x = 1,016,114.54/1,142.05
6. Step 6: Final answer
   x = 889.73