Finding the Fourth Proportional to 498.01, 687.59 and 311.78

Step by Step Solution

1. Step 1: Write the proportion equation
   498.01 : 687.59 = 311.78 : x
2. Step 2: Convert to fraction form
   498.01/687.59 = 311.78/x
3. Step 3: Cross multiply
   498.01x = 687.59 × 311.78
4. Step 4: Simplify right side
   498.01x = 214,376.81
5. Step 5: Solve for x
   x = 214,376.81/498.01
6. Step 6: Final answer
   x = 430.47