Finding the Fourth Proportional to 498.47, 687.92 and 288.72

Step by Step Solution

1. Step 1: Write the proportion equation
   498.47 : 687.92 = 288.72 : x
2. Step 2: Convert to fraction form
   498.47/687.92 = 288.72/x
3. Step 3: Cross multiply
   498.47x = 687.92 × 288.72
4. Step 4: Simplify right side
   498.47x = 198,614.82
5. Step 5: Solve for x
   x = 198,614.82/498.47
6. Step 6: Final answer
   x = 398.45