Finding the Third Proportional to 256.50 and 398.50

Step by Step Solution

1. Step 1: Write the proportion equation
   256.50 : 398.50 = 398.50 : x
2. Step 2: Convert to fraction form
   256.50/398.50 = 398.50/x
3. Step 3: Cross multiply
   256.50x = 398.50 × 398.50
4. Step 4: Simplify right side
   256.50x = 158,802.25
5. Step 5: Solve for x
   x = 158,802.25/256.50
6. Step 6: Final answer
   x = 619.11