Finding the Third Proportional to 287.72 and 430.31

Step by Step Solution

1. Step 1: Write the proportion equation
   287.72 : 430.31 = 430.31 : x
2. Step 2: Convert to fraction form
   287.72/430.31 = 430.31/x
3. Step 3: Cross multiply
   287.72x = 430.31 × 430.31
4. Step 4: Simplify right side
   287.72x = 185,168.85
5. Step 5: Solve for x
   x = 185,168.85/287.72
6. Step 6: Final answer
   x = 643.58