Finding the Fourth Proportional to 1,142.18, 1,576.20 and 644.81

Step by Step Solution

1. Step 1: Write the proportion equation
   1,142.18 : 1,576.20 = 644.81 : x
2. Step 2: Convert to fraction form
   1,142.18/1,576.20 = 644.81/x
3. Step 3: Cross multiply
   1,142.18x = 1,576.20 × 644.81
4. Step 4: Simplify right side
   1,142.18x = 1,016,341.64
5. Step 5: Solve for x
   x = 1,016,341.64/1,142.18
6. Step 6: Final answer
   x = 889.83