Finding the Fourth Proportional to 498.30, 687.72 and 288.50

Step by Step Solution

1. Step 1: Write the proportion equation
   498.30 : 687.72 = 288.50 : x
2. Step 2: Convert to fraction form
   498.30/687.72 = 288.50/x
3. Step 3: Cross multiply
   498.30x = 687.72 × 288.50
4. Step 4: Simplify right side
   498.30x = 198,403.78
5. Step 5: Solve for x
   x = 198,403.78/498.30
6. Step 6: Final answer
   x = 398.16