Finding the Fourth Proportional to 498.42, 687.96 and 288.63

Step by Step Solution

1. Step 1: Write the proportion equation
   498.42 : 687.96 = 288.63 : x
2. Step 2: Convert to fraction form
   498.42/687.96 = 288.63/x
3. Step 3: Cross multiply
   498.42x = 687.96 × 288.63
4. Step 4: Simplify right side
   498.42x = 198,565.89
5. Step 5: Solve for x
   x = 198,565.89/498.42
6. Step 6: Final answer
   x = 398.39