Finding the Third Proportional to 278.50 and 405.50

Step by Step Solution

1. Step 1: Write the proportion equation
   278.50 : 405.50 = 405.50 : x
2. Step 2: Convert to fraction form
   278.50/405.50 = 405.50/x
3. Step 3: Cross multiply
   278.50x = 405.50 × 405.50
4. Step 4: Simplify right side
   278.50x = 164,430.25
5. Step 5: Solve for x
   x = 164,430.25/278.50
6. Step 6: Final answer
   x = 590.41