Finding the Fourth Proportional to 498.69, 688.28 and 321.57

Step by Step Solution

1. Step 1: Write the proportion equation
   498.69 : 688.28 = 321.57 : x
2. Step 2: Convert to fraction form
   498.69/688.28 = 321.57/x
3. Step 3: Cross multiply
   498.69x = 688.28 × 321.57
4. Step 4: Simplify right side
   498.69x = 221,328.59
5. Step 5: Solve for x
   x = 221,328.59/498.69
6. Step 6: Final answer
   x = 443.82