Finding the Fourth Proportional to 498.21, 687.59 and 285.55

Step by Step Solution

1. Step 1: Write the proportion equation
   498.21 : 687.59 = 285.55 : x
2. Step 2: Convert to fraction form
   498.21/687.59 = 285.55/x
3. Step 3: Cross multiply
   498.21x = 687.59 × 285.55
4. Step 4: Simplify right side
   498.21x = 196,341.32
5. Step 5: Solve for x
   x = 196,341.32/498.21
6. Step 6: Final answer
   x = 394.09