Finding the Fourth Proportional to 1,086.72, 1,499.76 and 644.64

Step by Step Solution

1. Step 1: Write the proportion equation
   1,086.72 : 1,499.76 = 644.64 : x
2. Step 2: Convert to fraction form
   1,086.72/1,499.76 = 644.64/x
3. Step 3: Cross multiply
   1,086.72x = 1,499.76 × 644.64
4. Step 4: Simplify right side
   1,086.72x = 966,805.29
5. Step 5: Solve for x
   x = 966,805.29/1,086.72
6. Step 6: Final answer
   x = 889.65