Finding the Fourth Proportional to 1,086.89, 1,499.92 and 644.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,086.89 : 1,499.92 = 644.79 : x
2. Step 2: Convert to fraction form
   1,086.89/1,499.92 = 644.79/x
3. Step 3: Cross multiply
   1,086.89x = 1,499.92 × 644.79
4. Step 4: Simplify right side
   1,086.89x = 967,124.77
5. Step 5: Solve for x
   x = 967,124.77/1,086.89
6. Step 6: Final answer
   x = 889.81