Finding the Fourth Proportional to 1,086.88, 1,499.96 and 644.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,086.88 : 1,499.96 = 644.76 : x
2. Step 2: Convert to fraction form
   1,086.88/1,499.96 = 644.76/x
3. Step 3: Cross multiply
   1,086.88x = 1,499.96 × 644.76
4. Step 4: Simplify right side
   1,086.88x = 967,114.21
5. Step 5: Solve for x
   x = 967,114.21/1,086.88
6. Step 6: Final answer
   x = 889.81