Finding the Fourth Proportional to 1,142.05, 1,576.10 and 644.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,142.05 : 1,576.10 = 644.50 : x
2. Step 2: Convert to fraction form
   1,142.05/1,576.10 = 644.50/x
3. Step 3: Cross multiply
   1,142.05x = 1,576.10 × 644.50
4. Step 4: Simplify right side
   1,142.05x = 1,015,797.17
5. Step 5: Solve for x
   x = 1,015,797.17/1,142.05
6. Step 6: Final answer
   x = 889.45