Finding the Fourth Proportional to 498.78, 688.34 and 312.37

Step by Step Solution

1. Step 1: Write the proportion equation
   498.78 : 688.34 = 312.37 : x
2. Step 2: Convert to fraction form
   498.78/688.34 = 312.37/x
3. Step 3: Cross multiply
   498.78x = 688.34 × 312.37
4. Step 4: Simplify right side
   498.78x = 215,015.83
5. Step 5: Solve for x
   x = 215,015.83/498.78
6. Step 6: Final answer
   x = 431.08