Finding the Third Proportional to 287.23 and 429.72

Step by Step Solution

1. Step 1: Write the proportion equation
   287.23 : 429.72 = 429.72 : x
2. Step 2: Convert to fraction form
   287.23/429.72 = 429.72/x
3. Step 3: Cross multiply
   287.23x = 429.72 × 429.72
4. Step 4: Simplify right side
   287.23x = 184,658.20
5. Step 5: Solve for x
   x = 184,658.20/287.23
6. Step 6: Final answer
   x = 642.88