Finding the Third Proportional to 128,585 and 286,978

Step by Step Solution

1. Step 1: Write the proportion equation
   128,585 : 286,978 = 286,978 : x
2. Step 2: Convert to fraction form
   128,585/286,978 = 286,978/x
3. Step 3: Cross multiply
   128,585x = 286,978 × 286,978
4. Step 4: Simplify right side
   128,585x = 82,356,372,484
5. Step 5: Solve for x
   x = 82,356,372,484/128,585
6. Step 6: Final answer
   x = 640,481.96