Finding the Third Proportional to 390.50 and 498.50

Step by Step Solution

1. Step 1: Write the proportion equation
   390.50 : 498.50 = 498.50 : x
2. Step 2: Convert to fraction form
   390.50/498.50 = 498.50/x
3. Step 3: Cross multiply
   390.50x = 498.50 × 498.50
4. Step 4: Simplify right side
   390.50x = 248,502.25
5. Step 5: Solve for x
   x = 248,502.25/390.50
6. Step 6: Final answer
   x = 636.37