Finding the Fourth Proportional to 1,086.24, 1,499.28 and 644.64

Step by Step Solution

1. Step 1: Write the proportion equation
   1,086.24 : 1,499.28 = 644.64 : x
2. Step 2: Convert to fraction form
   1,086.24/1,499.28 = 644.64/x
3. Step 3: Cross multiply
   1,086.24x = 1,499.28 × 644.64
4. Step 4: Simplify right side
   1,086.24x = 966,495.86
5. Step 5: Solve for x
   x = 966,495.86/1,086.24
6. Step 6: Final answer
   x = 889.76